.. index:: single: PyBufferProcs
-More information on the buffer interface is provided in the section
+More information on the buffer interface is provided in the section
:ref:`buffer-structs`, under the description for :ctype:`PyBufferProcs`.
Buffer objects are useful as a way to expose the data from another object's
pointer += strides[i] * indices[i];
if (suboffsets[i] >=0 ) {
pointer = *((char**)pointer) + suboffsets[i];
- }
+ }
}
return (void*)pointer;
}
See the Unix man page :manpage:`atof(2)` for details.
-
+
.. cfunction:: char * PyOS_stricmp(char *s1, char *s2)
Case insensitive comparison of strings. The function works almost
.. warning::
- Take care when you are mixing streams and descriptors! For more
+ Take care when you are mixing streams and descriptors! For more
information, see `the GNU C Library docs
<http://www.gnu.org/software/libc/manual/html_node/Stream_002fDescriptor-Precautions.html#Stream_002fDescriptor-Precautions>`_.
Return a tuple of function call counts. There are constants defined for the
positions within the tuple:
-
+
+-------------------------------+-------+
| Name | Value |
+===============================+=======+
+-------------------------------+-------+
| :const:`PCALL_POP` | 10 |
+-------------------------------+-------+
-
+
:const:`PCALL_FAST_FUNCTION` means no argument tuple needs to be created.
:const:`PCALL_FASTER_FUNCTION` means that the fast-path frame setup code is used.
retrieved from the resulting value using :cfunc:`PyLong_AsVoidPtr`.
-.. XXX alias PyLong_AS_LONG (for now)
+.. XXX alias PyLong_AS_LONG (for now)
.. cfunction:: long PyLong_AsLong(PyObject *pylong)
.. index::
Return a C :ctype:`long` representation of the contents of *pylong*. If
*pylong* is greater than :const:`LONG_MAX`, return -1 and
- set `*overflow` to 1 (for overflow) or -1 (for underflow).
+ set `*overflow` to 1 (for overflow) or -1 (for underflow).
If an exception is set because of type errors, also return -1.
.. cfunction:: int PyModule_AddIntMacro(PyObject *module, macro)
- Add an int constant to *module*. The name and the value are taken from
+ Add an int constant to *module*. The name and the value are taken from
*macro*. For example ``PyModule_AddConstant(module, AF_INET)`` adds the int
constant *AF_INET* with the value of *AF_INET* to *module*.
Return ``-1`` on error, ``0`` on success.
Return a dictionary of the local variables in the current execution frame,
or *NULL* if no frame is currently executing.
-
+
.. cfunction:: PyObject* PyEval_GetGlobals()
Return the underlying array of PyObject pointers. Assumes that *o* was returned
by :cfunc:`PySequence_Fast` and *o* is not *NULL*.
-
+
Note, if a list gets resized, the reallocation may relocate the items array.
- So, only use the underlying array pointer in contexts where the sequence
+ So, only use the underlying array pointer in contexts where the sequence
cannot change.
| *package_dir* | A mapping of package to | a dictionary |
| | directory names | |
+--------------------+--------------------------------+-------------------------------------------------------------+
-
+
.. function:: run_setup(script_name[, script_args=None, stop_after='run'])
standard output, otherwise do nothing.
.. % \subsection{Compiler-specific modules}
-.. %
+.. %
.. % The following modules implement concrete subclasses of the abstract
.. % \class{CCompiler} class. They should not be instantiated directly, but should
.. % be created using \function{distutils.ccompiler.new_compiler()} factory
Macintosh. Needs work to support CW on Windows or Mac OS X.
.. % \subsection{Utility modules}
-.. %
+.. %
.. % The following modules all provide general utility functions. They haven't
.. % all been documented yet.
For MacOS X systems the OS version reflects the minimal version on which
binaries will run (that is, the value of ``MACOSX_DEPLOYMENT_TARGET``
- during the build of Python), not the OS version of the current system.
+ during the build of Python), not the OS version of the current system.
For universal binary builds on MacOS X the architecture value reflects
the univeral binary status instead of the architecture of the current
- processor. For 32-bit universal binaries the architecture is ``fat``,
- for 64-bit universal binaries the architecture is ``fat64``, and
- for 4-way universal binaries the architecture is ``universal``.
+ processor. For 32-bit universal binaries the architecture is ``fat``,
+ for 64-bit universal binaries the architecture is ``fat64``, and
+ for 4-way universal binaries the architecture is ``universal``.
Examples of returned values on MacOS X:
.. % todo
.. % \section{Distutils Commands}
-.. %
+.. %
.. % This part of Distutils implements the various Distutils commands, such
.. % as \code{build}, \code{install} \&c. Each command is implemented as a
.. % separate module, with the command name as the name of the module.
.. % \longprogramopt{spec-file} option; used in conjunction with
.. % \longprogramopt{spec-only}, this gives you an opportunity to customize
.. % the \file{.spec} file manually:
-.. %
+.. %
.. % \ begin{verbatim}
.. % > python setup.py bdist_rpm --spec-only
.. % # ...edit dist/FooBar-1.0.spec
.. % > python setup.py bdist_rpm --spec-file=dist/FooBar-1.0.spec
.. % \ end{verbatim}
-.. %
+.. %
.. % (Although a better way to do this is probably to override the standard
.. % \command{bdist\_rpm} command with one that writes whatever else you want
.. % to the \file{.spec} file.)
Cross-compiling on Windows
==========================
-Starting with Python 2.6, distutils is capable of cross-compiling between
-Windows platforms. In practice, this means that with the correct tools
+Starting with Python 2.6, distutils is capable of cross-compiling between
+Windows platforms. In practice, this means that with the correct tools
installed, you can use a 32bit version of Windows to create 64bit extensions
and vice-versa.
-To build for an alternate platform, specify the :option:`--plat-name` option
-to the build command. Valid values are currently 'win32', 'win-amd64' and
+To build for an alternate platform, specify the :option:`--plat-name` option
+to the build command. Valid values are currently 'win32', 'win-amd64' and
'win-ia64'. For example, on a 32bit version of Windows, you could execute::
python setup.py build --plat-name=win-amd64
-to build a 64bit version of your extension. The Windows Installers also
+to build a 64bit version of your extension. The Windows Installers also
support this option, so the command::
python setup.py build --plat-name=win-amd64 bdist_wininst
would create a 64bit installation executable on your 32bit version of Windows.
-To cross-compile, you must download the Python source code and cross-compile
+To cross-compile, you must download the Python source code and cross-compile
Python itself for the platform you are targetting - it is not possible from a
binary installtion of Python (as the .lib etc file for other platforms are
-not included.) In practice, this means the user of a 32 bit operating
-system will need to use Visual Studio 2008 to open the
-:file:`PCBuild/PCbuild.sln` solution in the Python source tree and build the
-"x64" configuration of the 'pythoncore' project before cross-compiling
+not included.) In practice, this means the user of a 32 bit operating
+system will need to use Visual Studio 2008 to open the
+:file:`PCBuild/PCbuild.sln` solution in the Python source tree and build the
+"x64" configuration of the 'pythoncore' project before cross-compiling
extensions is possible.
Note that by default, Visual Studio 2008 does not install 64bit compilers or
--include-dirs (-I) list of directories to search for header files
--define (-D) C preprocessor macros to define
--undef (-U) C preprocessor macros to undefine
- --swig-opts list of SWIG command line options
+ --swig-opts list of SWIG command line options
[...]
Note that an option spelled :option:`--foo-bar` on the command-line is spelled
index-servers =
pypi
other
-
+
[pypi]
repository: <repository-url>
username: <username>
python setup.py register -r other
-
+
this::
setup(...,
- ext_modules=[Extension('_foo', ['foo.i'],
+ ext_modules=[Extension('_foo', ['foo.i'],
swig_opts=['-modern', '-I../include'])],
py_modules=['foo'],
)
curly braces to indicate a "variable" part, as in ``:file:``.
If you don't need the "variable part" indication, use the standard
- ````code```` instead.
+ ````code```` instead.
.. describe:: var
don't have to escape ``*`` or ``|`` characters.
-.. XXX describe optional first parameter
+.. XXX describe optional first parameter
The following is an example taken from the Python Reference Manual::
With this :file:`setup.py`, and a file :file:`demo.c`, running ::
- python setup.py build
+ python setup.py build
will compile :file:`demo.c`, and produce an extension module named ``demo`` in
the :file:`build` directory. Depending on the system, the module file will end
:cfunc:`PyInit_spam` is called. (See below for comments about embedding Python.)
It calls :cfunc:`PyModule_Create`, which returns a module object, and
inserts built-in function objects into the newly created module based upon the
-table (an array of :ctype:`PyMethodDef` structures) found in the module definition.
+table (an array of :ctype:`PyMethodDef` structures) found in the module definition.
:cfunc:`PyModule_Create` returns a pointer to the module object
that it creates. It may abort with a fatal error for
certain errors, or return *NULL* if the module could not be initialized
:cfunc:`PyEval_CallObject`. This function has two arguments, both pointers to
arbitrary Python objects: the Python function, and the argument list. The
argument list must always be a tuple object, whose length is the number of
-arguments. To call the Python function with no arguments, pass in NULL, or
+arguments. To call the Python function with no arguments, pass in NULL, or
an empty tuple; to call it with one argument, pass a singleton tuple.
:cfunc:`Py_BuildValue` returns a tuple when its format string consists of zero
or more format codes between parentheses. For example::
if (result == NULL)
return NULL; /* Pass error back */
...use result...
- Py_DECREF(result);
+ Py_DECREF(result);
Depending on the desired interface to the Python callback function, you may also
have to provide an argument list to :cfunc:`PyEval_CallObject`. In some cases
the error check! Also note that strictly speaking this code is not complete:
:cfunc:`Py_BuildValue` may run out of memory, and this should be checked.
-You may also call a function with keyword arguments by using
+You may also call a function with keyword arguments by using
:cfunc:`PyEval_CallObjectWithKeywords`. As in the above example, we use
:cfunc:`Py_BuildValue` to construct the dictionary. ::
static PyObject *
keywdarg_parrot(PyObject *self, PyObject *args, PyObject *keywds)
- {
+ {
int voltage;
char *state = "a stiff";
char *action = "voom";
static char *kwlist[] = {"voltage", "state", "action", "type", NULL};
- if (!PyArg_ParseTupleAndKeywords(args, keywds, "i|sss", kwlist,
+ if (!PyArg_ParseTupleAndKeywords(args, keywds, "i|sss", kwlist,
&voltage, &state, &action, &type))
- return NULL;
+ return NULL;
- printf("-- This parrot wouldn't %s if you put %i Volts through it.\n",
+ printf("-- This parrot wouldn't %s if you put %i Volts through it.\n",
action, voltage);
printf("-- Lovely plumage, the %s -- It's %s!\n", type, state);
of *NULL* is required.
.. XXX Descriptors need to be explained in more detail somewhere, but not here.
-
+
Descriptor objects have two handler functions which correspond to the
\member{tp_getattro} and \member{tp_setattro} handlers. The
\method{__get__()} handler is a function which is passed the descriptor,
return -1;
}
-.. XXX tp_compare is dead; need to rewrite for tp_richcompare!
+.. XXX tp_compare is dead; need to rewrite for tp_richcompare!
Object Comparison
-----------------
-
+
::
-
+
cmpfunc tp_compare;
-
+
The :attr:`tp_compare` handler is called when comparisons are needed and the
object does not implement the specific rich comparison method which matches the
requested comparison. (It is always used if defined and the
allowed to return arbitrary negative or positive integers for less than and
greater than, respectively; as of Python 2.2, this is no longer allowed. In the
future, other return values may be assigned a different meaning.)
-
+
A :attr:`tp_compare` handler may raise an exception. In this case it should
return a negative value. The caller has to test for the exception using
:cfunc:`PyErr_Occurred`.
-
+
Here is a sample implementation::
-
+
static int
newdatatype_compare(newdatatypeobject * obj1, newdatatypeobject * obj2)
{
long result;
-
+
if (obj1->obj_UnderlyingDatatypePtr->size <
obj2->obj_UnderlyingDatatypePtr->size) {
result = -1;
and it should call :cfunc:`Py_InitModule` with the string ``"spam"`` as its
first argument (use the minimal :file:`example.c` in this directory as a guide).
By convention, it lives in a file called :file:`spam.c` or :file:`spammodule.c`.
- The output file should be called :file:`spam.pyd` (in Release mode) or
+ The output file should be called :file:`spam.pyd` (in Release mode) or
:file:`spam_d.pyd` (in Debug mode). The extension :file:`.pyd` was chosen
to avoid confusion with a system library :file:`spam.dll` to which your module
could be a Python interface.
``>>>``
The default Python prompt of the interactive shell. Often seen for code
examples which can be executed interactively in the interpreter.
-
+
``...``
The default Python prompt of the interactive shell when entering code for
an indented code block or within a pair of matching left and right
A value associated with an object which is referenced by name using
dotted expressions. For example, if an object *o* has an attribute
*a* it would be referenced as *o.a*.
-
+
BDFL
Benevolent Dictator For Life, a.k.a. `Guido van Rossum
<http://www.python.org/~guido/>`_, Python's creator.
-
+
bytecode
Python source code is compiled into bytecode, the internal representation
of a Python program in the interpreter. The bytecode is also cached in
A template for creating user-defined objects. Class definitions
normally contain method definitions which operate on instances of the
class.
-
+
coercion
The implicit conversion of an instance of one type to another during an
operation which involves two arguments of the same type. For example,
will raise a ``TypeError``. Without coercion, all arguments of even
compatible types would have to be normalized to the same value by the
programmer, e.g., ``float(3)+4.5`` rather than just ``3+4.5``.
-
+
complex number
An extension of the familiar real number system in which all numbers are
expressed as a sum of a real part and an imaginary part. Imaginary
:mod:`math` module, use :mod:`cmath`. Use of complex numbers is a fairly
advanced mathematical feature. If you're not aware of a need for them,
it's almost certain you can safely ignore them.
-
+
context manager
An object which controls the environment seen in a :keyword:`with`
statement by defining :meth:`__enter__` and :meth:`__exit__` methods.
and reference to super classes.
For more information about descriptors' methods, see :ref:`descriptors`.
-
+
dictionary
An associative array, where arbitrary keys are mapped to values. The use
of :class:`dict` closely resembles that for :class:`list`, but the keys can
of the enclosing class, function or module. Since it is available via
introspection, it is the canonical place for documentation of the
object.
-
- duck-typing
+
+ duck-typing
A pythonic programming style which determines an object's type by inspection
of its method or attribute signature rather than by explicit relationship
to some type object ("If it looks like a duck and quacks like a duck, it
:func:`isinstance`. (Note, however, that duck-typing can be complemented
with abstract base classes.) Instead, it typically employs :func:`hasattr`
tests or :term:`EAFP` programming.
-
+
EAFP
Easier to ask for forgiveness than permission. This common Python coding
style assumes the existence of valid keys or attributes and catches
exceptions if the assumption proves false. This clean and fast style is
characterized by the presence of many :keyword:`try` and :keyword:`except`
- statements. The technique contrasts with the :term:`LBYL` style
+ statements. The technique contrasts with the :term:`LBYL` style
common to many other languages such as C.
expression
By importing the :mod:`__future__` module and evaluating its variables,
you can see when a new feature was first added to the language and when it
becomes the default::
-
+
>>> import __future__
>>> __future__.division
_Feature((2, 2, 0, 'alpha', 2), (3, 0, 0, 'alpha', 0), 8192)
The process of freeing memory when it is not used anymore. Python
performs garbage collection via reference counting and a cyclic garbage
collector that is able to detect and break reference cycles.
-
+
generator
A function which returns an iterator. It looks like a normal function
except that values are returned to the caller using a :keyword:`yield`
stopped at the :keyword:`yield` keyword (returning the result) and is
resumed there when the next element is requested by calling the
:meth:`__next__` method of the returned iterator.
-
+
.. index:: single: generator expression
-
+
generator expression
An expression that returns a generator. It looks like a normal expression
followed by a :keyword:`for` expression defining a loop variable, range,
and an optional :keyword:`if` expression. The combined expression
generates values for an enclosing function::
-
+
>>> sum(i*i for i in range(10)) # sum of squares 0, 1, 4, ... 81
285
-
+
GIL
See :term:`global interpreter lock`.
-
+
global interpreter lock
The lock used by Python threads to assure that only one thread
executes in the :term:`CPython` :term:`virtual machine` at a time.
containers (such as lists or dictionaries) are. Objects which are
instances of user-defined classes are hashable by default; they all
compare unequal, and their hash value is their :func:`id`.
-
+
IDLE
An Integrated Development Environment for Python. IDLE is a basic editor
and interpreter environment which ships with the standard distribution of
Python. Good for beginners, it also serves as clear example code for
those wanting to implement a moderately sophisticated, multi-platform GUI
application.
-
+
immutable
An object with a fixed value. Immutable objects include numbers, strings and
tuples. Such an object cannot be altered. A new object has to
arguments (possibly by selecting it from your computer's main
menu). It is a very powerful way to test out new ideas or inspect
modules and packages (remember ``help(x)``).
-
+
interpreted
Python is an interpreted language, as opposed to a compiled one,
though the distinction can be blurry because of the presence of the
Interpreted languages typically have a shorter development/debug cycle
than compiled ones, though their programs generally also run more
slowly. See also :term:`interactive`.
-
+
iterable
A container object capable of returning its members one at a
time. Examples of iterables include all sequence types (such as
statement does that automatically for you, creating a temporary unnamed
variable to hold the iterator for the duration of the loop. See also
:term:`iterator`, :term:`sequence`, and :term:`generator`.
-
+
iterator
An object representing a stream of data. Repeated calls to the iterator's
:meth:`__next__` (or passing it to the builtin function) :func:`next`
:func:`iter` function or use it in a :keyword:`for` loop. Attempting this
with an iterator will just return the same exhausted iterator object used
in the previous iteration pass, making it appear like an empty container.
-
+
More information can be found in :ref:`typeiter`.
keyword argument
A built-in Python :term:`sequence`. Despite its name it is more akin
to an array in other languages than to a linked list since access to
elements are O(1).
-
+
list comprehension
A compact way to process all or part of the elements in a sequence and
return a list with the results. ``result = ["0x%02x" % x for x in
even hex numbers (0x..) in the range from 0 to 255. The :keyword:`if`
clause is optional. If omitted, all elements in ``range(256)`` are
processed.
-
+
mapping
A container object (such as :class:`dict`) which supports arbitrary key
lookups using the special method :meth:`__getitem__`.
-
+
metaclass
The class of a class. Class definitions create a class name, a class
dictionary, and a list of base classes. The metaclass is responsible for
of an instance of that class, the method will get the instance object as
its first :term:`argument` (which is usually called ``self``).
See :term:`function` and :term:`nested scope`.
-
+
mutable
Mutable objects can change their value but keep their :func:`id`. See
also :term:`immutable`.
:func:`collections.namedtuple`. The latter approach automatically
provides extra features such as a self-documenting representation like
``Employee(name='jones', title='programmer')``.
-
+
namespace
The place where a variable is stored. Namespaces are implemented as
dictionaries. There are the local, global and builtin namespaces as well
:func:`random.seed` or :func:`itertools.izip` makes it clear that those
functions are implemented by the :mod:`random` and :mod:`itertools`
modules, respectively.
-
+
nested scope
The ability to refer to a variable in an enclosing definition. For
instance, a function defined inside another function can refer to
reference and not for assignment which will always write to the innermost
scope. In contrast, local variables both read and write in the innermost
scope. Likewise, global variables read and write to the global namespace.
-
+
new-style class
Old name for the flavor of classes now used for all class objects. In
earlier Python versions, only new-style classes could use Python's newer,
Any data with state (attributes or value) and defined behavior
(methods). Also the ultimate base class of any :term:`new-style
class`.
-
+
positional argument
The arguments assigned to local names inside a function or method,
determined by the order in which they were given in the call. ``*`` is
to loop over all elements of an iterable using a :keyword:`for`
statement. Many other languages don't have this type of construct, so
people unfamiliar with Python sometimes use a numerical counter instead::
-
+
for i in range(len(food)):
print(food[i])
popular, the technique is somewhat tricky to get right and is best
reserved for rare cases where there are large numbers of instances in a
memory-critical application.
-
+
sequence
An :term:`iterable` which supports efficient element access using integer
indices via the :meth:`__getitem__` special method and defines a
virtual machine
A computer defined entirely in software. Python's virtual machine
executes the :term:`bytecode` emitted by the bytecode compiler.
-
+
Zen of Python
Listing of Python design principles and philosophies that are helpful in
understanding and using the language. The listing can be found by typing
curses.echo() # Enable echoing of characters
- # Get a 15-character string, with the cursor on the top line
- s = stdscr.getstr(0,0, 15)
+ # Get a 15-character string, with the cursor on the top line
+ s = stdscr.getstr(0,0, 15)
The Python :mod:`curses.textpad` module supplies something better. With it, you
can turn a window into a text box that supports an Emacs-like set of
************************************
- Idioms and Anti-Idioms in Python
+ Idioms and Anti-Idioms in Python
************************************
:Author: Moshe Zadka
# bar.py
from foo import a
if something():
- a = 2 # danger: foo.a != a
+ a = 2 # danger: foo.a != a
Good example::
This version is bulletproof::
- value = (foo.bar()['first'][0]*baz.quux(1, 2)[5:9]
+ value = (foo.bar()['first'][0]*baz.quux(1, 2)[5:9]
+ calculate_number(10, 20)*forbulate(500, 360))
functions are also easier to read and to check for errors.
-Ease of debugging and testing
+Ease of debugging and testing
-----------------------------
Testing and debugging a functional-style program is easier.
Traceback (most recent call last):
File "<stdin>", line 1, in ?
StopIteration
- >>>
+ >>>
Python expects iterable objects in several different contexts, the most
important being the ``for`` statement. In the statement ``for X in Y``, Y must
comprehensions are surrounded by square brackets ("[]"). Generator expressions
have the form::
- ( expression for expr in sequence1
+ ( expression for expr in sequence1
if condition1
for expr2 in sequence2
if condition2
if not (conditionN):
continue # Skip this element
- # Output the value of
+ # Output the value of
# the expression.
This means that when there are multiple ``for...in`` clauses but no ``if``
>>> seq1 = 'abc'
>>> seq2 = (1,2,3)
>>> [(x,y) for x in seq1 for y in seq2]
- [('a', 1), ('a', 2), ('a', 3),
- ('b', 1), ('b', 2), ('b', 3),
+ [('a', 1), ('a', 2), ('a', 3),
+ ('b', 1), ('b', 2), ('b', 3),
('c', 1), ('c', 2), ('c', 3)]
To avoid introducing an ambiguity into Python's grammar, if ``expression`` is
Two of Python's built-in functions, :func:`map` and :func:`filter` duplicate the
features of generator expressions:
-``map(f, iterA, iterB, ...)`` returns an iterator over the sequence
+``map(f, iterA, iterB, ...)`` returns an iterator over the sequence
``f(iterA[0], iterB[0]), f(iterA[1], iterB[1]), f(iterA[2], iterB[2]), ...``.
>>> def upper(s):
>>> [upper(s) for s in ['sentence', 'fragment']]
['SENTENCE', 'FRAGMENT']
-You can of course achieve the same effect with a list comprehension.
+You can of course achieve the same effect with a list comprehension.
``filter(predicate, iter)`` returns an iterator over all the sequence elements
that meet a certain condition, and is similarly duplicated by list
True
>>> all([0,1,0])
False
- >>> all([0,0,0])
+ >>> all([0,0,0])
False
>>> all([1,1,1])
True
``itertools.starmap(func, iter)`` assumes that the iterable will return a stream
of tuples, and calls ``f()`` using these tuples as the arguments::
- itertools.starmap(os.path.join,
+ itertools.starmap(os.path.join,
[('/usr', 'bin', 'java'), ('/bin', 'python'),
('/usr', 'bin', 'perl'),('/usr', 'bin', 'ruby')])
=>
::
- city_list = [('Decatur', 'AL'), ('Huntsville', 'AL'), ('Selma', 'AL'),
+ city_list = [('Decatur', 'AL'), ('Huntsville', 'AL'), ('Selma', 'AL'),
('Anchorage', 'AK'), ('Nome', 'AK'),
- ('Flagstaff', 'AZ'), ('Phoenix', 'AZ'), ('Tucson', 'AZ'),
+ ('Flagstaff', 'AZ'), ('Phoenix', 'AZ'), ('Tucson', 'AZ'),
...
]
where
iterator-1 =>
('Decatur', 'AL'), ('Huntsville', 'AL'), ('Selma', 'AL')
- iterator-2 =>
+ iterator-2 =>
('Anchorage', 'AK'), ('Nome', 'AK')
iterator-3 =>
('Flagstaff', 'AZ'), ('Phoenix', 'AZ'), ('Tucson', 'AZ')
>>> double(add(5, 6))
22
-
+
The ``unpack`` keyword is provided to work around the fact that Python functions
are not always `fully curried <http://en.wikipedia.org/wiki/Currying>`__. By
default, it is expected that the ``inner`` function will return a single object
will be expanded before being passed to ``outer``. Put simply, ::
compose(f, g)(5, 6)
-
+
is equivalent to::
f(g(5, 6))
-
+
while ::
compose(f, g, unpack=True)(5, 6)
-
+
is equivalent to::
f(*g(5, 6))
from functional import compose, partial
import functools
-
+
multi_compose = partial(functools.reduce, compose)
-
-
+
+
We can also use ``map()``, ``compose()`` and ``partial()`` to craft a version of
``"".join(...)`` that converts its arguments to string::
from functional import compose, partial
-
+
join = compose("".join, partial(map, str))
``flip(func)``
-
+
``flip()`` wraps the callable in ``func`` and causes it to receive its
non-keyword arguments in reverse order. ::
(7, 6, 5)
``foldl(func, start, iterable)``
-
+
``foldl()`` takes a binary function, a starting value (usually some kind of
'zero'), and an iterable. The function is applied to the starting value and the
first element of the list, then the result of that and the second element of the
f(f(f(0, 1), 2), 3)
-
+
``foldl()`` is roughly equivalent to the following recursive function::
def foldl(func, start, seq):
4) Convert the lambda to a def statement, using that name.
5) Remove the comment.
-I really like these rules, but you're free to disagree
+I really like these rules, but you're free to disagree
about whether this lambda-free style is better.
Text Processing".
Mertz also wrote a 3-part series of articles on functional programming
-for IBM's DeveloperWorks site; see
+for IBM's DeveloperWorks site; see
`part 1 <http://www-128.ibm.com/developerworks/library/l-prog.html>`__,
`part 2 <http://www-128.ibm.com/developerworks/library/l-prog2.html>`__, and
`part 3 <http://www-128.ibm.com/developerworks/linux/library/l-prog3.html>`__,
****************************
- Socket Programming HOWTO
+ Socket Programming HOWTO
****************************
:Author: Gordon McMillan
#create an INET, STREAMing socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
- #now connect to the web server on port 80
+ #now connect to the web server on port 80
# - the normal http port
s.connect(("www.mcmillan-inc.com", 80))
#create an INET, STREAMing socket
serversocket = socket.socket(
socket.AF_INET, socket.SOCK_STREAM)
- #bind the socket to a public host,
+ #bind the socket to a public host,
# and a well-known port
serversocket.bind((socket.gethostname(), 80))
#become a server socket
length message::
class mysocket:
- """demonstration class only
+ """demonstration class only
- coded for clarity, not efficiency
"""
ready_to_read, ready_to_write, in_error = \
select.select(
- potential_readers,
- potential_writers,
- potential_errs,
+ potential_readers,
+ potential_writers,
+ potential_errs,
timeout)
You pass ``select`` three lists: the first contains all sockets that you might
HOWTO, available at `urllib2 - Le Manuel manquant
<http://www.voidspace.org.uk/python/articles/urllib2_francais.shtml>`_.
-
+
Introduction
============
You may also find useful the following article on fetching web resources
with Python:
-
+
* `Basic Authentication <http://www.voidspace.org.uk/python/articles/authentication.shtml>`_
-
+
A tutorial on *Basic Authentication*, with examples in Python.
**urllib.request** is a `Python <http://www.python.org>`_ module for fetching URLs
library. ::
import urllib.parse
- import urllib.request
+ import urllib.request
url = 'http://www.someserver.com/cgi-bin/register.cgi'
values = {'name' : 'Michael Foord',
Explorer [#]_. ::
import urllib.parse
- import urllib.request
-
+ import urllib.request
+
url = 'http://www.someserver.com/cgi-bin/register.cgi'
- user_agent = 'Mozilla/4.0 (compatible; MSIE 5.5; Windows NT)'
+ user_agent = 'Mozilla/4.0 (compatible; MSIE 5.5; Windows NT)'
values = {'name' : 'Michael Foord',
'location' : 'Northampton',
'language' : 'Python' }
headers = { 'User-Agent' : user_agent }
-
+
data = urllib.parse.urlencode(values)
req = urllib.request.Request(url, data, headers)
response = urllib.request.urlopen(req)
===================
*urlopen* raises :exc:`URLError` when it cannot handle a response (though as usual
-with Python APIs, builtin exceptions such as
+with Python APIs, builtin exceptions such as
:exc:`ValueError`, :exc:`TypeError` etc. may also
be raised).
geturl, and info, methods as returned by the ``urllib.response`` module::
>>> req = urllib.request.Request('http://www.python.org/fish.html')
- >>> try:
+ >>> try:
>>> urllib.request.urlopen(req)
>>> except urllib.error.URLError, e:
>>> print(e.code)
>>> print(e.read())
- >>>
+ >>>
404
- <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
+ <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
- <?xml-stylesheet href="./css/ht2html.css"
+ <?xml-stylesheet href="./css/ht2html.css"
type="text/css"?>
- <html><head><title>Error 404: File Not Found</title>
+ <html><head><title>Error 404: File Not Found</title>
...... etc...
Wrapping it Up
print('Error code: ', e.code)
else:
# everything is fine
-
+
info and geturl
===============
and a 'realm'. The header looks like : ``Www-authenticate: SCHEME
realm="REALM"``.
-e.g. ::
+e.g. ::
Www-authenticate: Basic realm="cPanel Users"
than the URL you pass to .add_password() will also match. ::
# create a password manager
- password_mgr = urllib.request.HTTPPasswordMgrWithDefaultRealm()
+ password_mgr = urllib.request.HTTPPasswordMgrWithDefaultRealm()
# Add the username and password.
# If we knew the realm, we could use it instead of ``None``.
top_level_url = "http://example.com/foo/"
password_mgr.add_password(None, top_level_url, username, password)
- handler = urllib.request.HTTPBasicAuthHandler(password_mgr)
+ handler = urllib.request.HTTPBasicAuthHandler(password_mgr)
# create "opener" (OpenerDirector instance)
- opener = urllib.request.build_opener(handler)
+ opener = urllib.request.build_opener(handler)
# use the opener to fetch a URL
- opener.open(a_url)
+ opener.open(a_url)
# Install the opener.
# Now all calls to urllib.request.urlopen use our opener.
- urllib.request.install_opener(opener)
+ urllib.request.install_opener(opener)
.. note::
# timeout in seconds
timeout = 10
- socket.setdefaulttimeout(timeout)
+ socket.setdefaulttimeout(timeout)
# this call to urllib.request.urlopen now uses the default timeout
# we have set in the socket module
This document was reviewed and revised by John Lee.
.. [#] For an introduction to the CGI protocol see
- `Writing Web Applications in Python <http://www.pyzine.com/Issue008/Section_Articles/article_CGIOne.html>`_.
+ `Writing Web Applications in Python <http://www.pyzine.com/Issue008/Section_Articles/article_CGIOne.html>`_.
.. [#] Like Google for example. The *proper* way to use google from a program
is to use `PyGoogle <http://pygoogle.sourceforge.net>`_ of course. See
`Voidspace Google <http://www.voidspace.org.uk/python/recipebook.shtml#google>`_
is set to use the proxy, which urllib picks up on. In order to test
scripts with a localhost server, I have to prevent urllib from using
the proxy.
-.. [#] urllib opener for SSL proxy (CONNECT method): `ASPN Cookbook Recipe
+.. [#] urllib opener for SSL proxy (CONNECT method): `ASPN Cookbook Recipe
<http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/456195>`_.
-
+
<http://wiki.python.org/moin/CgiScripts>`_ with some additional information
about CGI in Python.
-
+
Simple script for testing CGI
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
You might be interested in some WSGI-supporting modules already contained in
the standard library, namely:
-
+
* :mod:`wsgiref` -- some tiny utilities and servers for WSGI
time in looking through the most popular ones. Some frameworks have their
own template engine or have a recommentation for one. It's wise to use
these.
-
+
Popular template engines include:
* Mako
found in the Python wiki.
.. seealso::
-
+
The Python wiki contains an extensive list of `web frameworks
<http://wiki.python.org/moin/WebFrameworks>`_.
.. _install-index:
*****************************
- Installing Python Modules
+ Installing Python Modules
*****************************
:Author: Greg Ward
Thus, I have to be sure to explain the basics at some point:
sys.path and PYTHONPATH at least. Should probably give pointers to
other docs on "import site", PYTHONSTARTUP, PYTHONHOME, etc.
-
+
Finally, it might be useful to include all the material from my "Care
and Feeding of a Python Installation" talk in here somewhere. Yow!
statements shown below, and get the output as shown, to find out my
:file:`{prefix}` and :file:`{exec-prefix}`::
- Python 2.4 (#26, Aug 7 2004, 17:19:02)
+ Python 2.4 (#26, Aug 7 2004, 17:19:02)
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.prefix
Type ``help'', ``copyright'', ``credits'' or ``license'' for more information.
>>> import sys
>>> sys.path
- ['', '/usr/local/lib/python2.3', '/usr/local/lib/python2.3/plat-linux2',
- '/usr/local/lib/python2.3/lib-tk', '/usr/local/lib/python2.3/lib-dynload',
+ ['', '/usr/local/lib/python2.3', '/usr/local/lib/python2.3/plat-linux2',
+ '/usr/local/lib/python2.3/lib-tk', '/usr/local/lib/python2.3/lib-dynload',
'/usr/local/lib/python2.3/site-packages']
>>>
A decorator indicating abstract methods.
Using this decorator requires that the class's metaclass is :class:`ABCMeta` or
- is derived from it.
+ is derived from it.
A class that has a metaclass derived from :class:`ABCMeta`
cannot be instantiated unless all of its abstract methods and
properties are overridden.
A subclass of the built-in :func:`property`, indicating an abstract property.
Using this function requires that the class's metaclass is :class:`ABCMeta` or
- is derived from it.
+ is derived from it.
A class that has a metaclass derived from :class:`ABCMeta` cannot be
instantiated unless all of its abstract methods and properties are overridden.
The abstract properties can be called using any of the normal
ability to compress the audio data.
.. warning::
-
+
Some operations may only work under IRIX; these will raise :exc:`ImportError`
when attempting to import the :mod:`cl` module, which is only available on IRIX.
Return a new array whose items are restricted by *typecode*, and initialized
from the optional *initializer* value, which must be a list, object
- supporting the buffer interface, or iterable over elements of the
+ supporting the buffer interface, or iterable over elements of the
appropriate type.
If given a list or string, the initializer is passed to the new array's
Parse an expression into an AST node. Equivalent to ``compile(expr,
filename, mode, ast.PyCF_ONLY_AST)``.
-
+
.. function:: literal_eval(node_or_string)
Safely evaluate an expression node or a string containing a Python
.. method:: generic_visit(node)
This visitor calls :meth:`visit` on all children of the node.
-
+
Note that child nodes of nodes that have a custom visitor method won't be
visited unless the visitor calls :meth:`generic_visit` or visits them
itself.
in_test = inputdata[pos*2:]
ipos, factor = audioop.findfit(in_test, out_test)
# Optional (for better cancellation):
- # factor = audioop.findfactor(in_test[ipos*2:ipos*2+len(out_test)],
+ # factor = audioop.findfactor(in_test[ipos*2:ipos*2+len(out_test)],
# out_test)
prefill = '\0'*(pos+ipos)*2
postfill = '\0'*(len(inputdata)-len(prefill)-len(outputdata))
Check whether we should break here, depending on the way the breakpoint *b*
was set.
-
+
If it was set via line number, it checks if ``b.line`` is the same as the one
in the frame also passed as argument. If the breakpoint was set via function
name, we have to check we are in the right frame (the right function) and if
.. function:: polar(x)
- Convert a :class:`complex` from rectangular coordinates to polar
+ Convert a :class:`complex` from rectangular coordinates to polar
coordinates. The function returns a tuple with the two elements
- *r* and *phi*. *r* is the distance from 0 and *phi* the phase
+ *r* and *phi*. *r* is the distance from 0 and *phi* the phase
angle.
other value will cause :exc:`ValueError` to be raised.
.. warning::
-
+
It is possible (but not likely) that the parser stops parsing with a
successful outcome before reaching the end of the source; in this case,
trailing symbols may be ignored instead of causing an error. For example,
:class:`Iterator` :class:`Iterable` ``__next__`` ``__iter__``
:class:`Sized` ``__len__``
:class:`Callable` ``__call__``
-
+
:class:`Sequence` :class:`Sized`, ``__getitem__`` ``__contains__``. ``__iter__``, ``__reversed__``.
:class:`Iterable`, and ``__len__`` ``index``, and ``count``
- :class:`Container`
-
+ :class:`Container`
+
:class:`MutableSequence` :class:`Sequence` ``__getitem__`` Inherited Sequence methods and
``__delitem__``, ``append``, ``reverse``, ``extend``, ``pop``,
``insert``, ``remove``, and ``__iadd__``
and ``__len__``
-
+
:class:`Set` :class:`Sized`, ``__len__``, ``__le__``, ``__lt__``, ``__eq__``, ``__ne__``,
:class:`Iterable`, ``__iter__``, and ``__gt__``, ``__ge__``, ``__and__``, ``__or__``
:class:`Container` ``__contains__`` ``__sub__``, ``__xor__``, and ``isdisjoint``
-
+
:class:`MutableSet` :class:`Set` ``add`` and Inherited Set methods and
``discard`` ``clear``, ``pop``, ``remove``, ``__ior__``,
``__iand__``, ``__ixor__``, and ``__isub__``
-
+
:class:`Mapping` :class:`Sized`, ``__getitem__``, ``__contains__``, ``keys``, ``items``, ``values``,
:class:`Iterable`, ``__len__``. and ``get``, ``__eq__``, and ``__ne__``
:class:`Container` ``__iter__``
-
+
:class:`MutableMapping` :class:`Mapping` ``__getitem__`` Inherited Mapping methods and
``__setitem__``, ``pop``, ``popitem``, ``clear``, ``update``,
``__delitem__``, and ``setdefault``
``__iter__``, and
``__len__``
-
+
:class:`MappingView` :class:`Sized` ``__len__``
:class:`KeysView` :class:`MappingView`, ``__contains__``,
:class:`Set` ``__iter__``
if kwds:
raise ValueError('Got unexpected field names: %r' % kwds.keys())
return result
- <BLANKLINE>
- def __getnewargs__(self):
+ <BLANKLINE>
+ def __getnewargs__(self):
return tuple(self)
<BLANKLINE>
x = property(itemgetter(0))
:class:`UserDict` objects
-------------------------
-The class, :class:`UserDict` acts as a wrapper around dictionary objects.
-The need for this class has been partially supplanted by the ability to
+The class, :class:`UserDict` acts as a wrapper around dictionary objects.
+The need for this class has been partially supplanted by the ability to
subclass directly from :class:`dict`; however, this class can be easier
to work with because the underlying dictionary is accessible as an
attribute.
initialized with its contents; note that a reference to *initialdata* will not
be kept, allowing it be used for other purposes.
-In addition to supporting the methods and operations of mappings,
+In addition to supporting the methods and operations of mappings,
:class:`UserDict` instances provide the following attribute:
.. attribute:: UserDict.data
-------------------------
This class acts as a wrapper around list objects. It is a useful base class
-for your own list-like classes which can inherit from them and override
+for your own list-like classes which can inherit from them and override
existing methods or add new ones. In this way, one can add new behaviors to
lists.
-The need for this class has been partially supplanted by the ability to
+The need for this class has been partially supplanted by the ability to
subclass directly from :class:`list`; however, this class can be easier
to work with because the underlying list is accessible as an attribute.
defaulting to the empty list ``[]``. *list* can be any iterable, for
example a real Python list or a :class:`UserList` object.
-In addition to supporting the methods and operations of mutable sequences,
+In addition to supporting the methods and operations of mutable sequences,
:class:`UserList` instances provide the following attribute:
.. attribute:: UserList.data
- A real :class:`list` object used to store the contents of the
+ A real :class:`list` object used to store the contents of the
:class:`UserList` class.
**Subclassing requirements:** Subclasses of :class:`UserList` are expect to
:class:`UserString` objects
---------------------------
-The class, :class:`UserString` acts as a wrapper around string objects.
-The need for this class has been partially supplanted by the ability to
+The class, :class:`UserString` acts as a wrapper around string objects.
+The need for this class has been partially supplanted by the ability to
subclass directly from :class:`str`; however, this class can be easier
to work with because the underlying string is accessible as an
attribute.
.. class:: UserString([sequence])
Class that simulates a string or a Unicode string object. The instance's
- content is kept in a regular string object, which is accessible via the
- :attr:`data` attribute of :class:`UserString` instances. The instance's
+ content is kept in a regular string object, which is accessible via the
+ :attr:`data` attribute of :class:`UserString` instances. The instance's
contents are initially set to a copy of *sequence*. The *sequence* can
be an instance of :class:`bytes`, :class:`str`, :class:`UserString` (or a
subclass) or an arbitrary sequence which can be converted into a string using
import configparser
config = configparser.RawConfigParser()
-
+
# When adding sections or items, add them in the reverse order of
# how you want them to be displayed in the actual file.
# In addition, please note that using RawConfigParser's and the raw
config.set('Section1', 'baz', 'fun')
config.set('Section1', 'bar', 'Python')
config.set('Section1', 'foo', '%(bar)s is %(baz)s!')
-
+
# Writing our configuration file to 'example.cfg'
with open('example.cfg', 'wb') as configfile:
config.write(configfile)
print(config.get('Section1', 'foo', 0, {'bar': 'Documentation',
'baz': 'evil'}))
-Defaults are available in all three types of ConfigParsers. They are used in
+Defaults are available in all three types of ConfigParsers. They are used in
interpolation if an option used is not defined elsewhere. ::
import configparser
# New instance with 'bar' and 'baz' defaulting to 'Life' and 'hard' each
config = configparser.SafeConfigParser({'bar': 'Life', 'baz': 'hard'})
config.read('example.cfg')
-
+
print(config.get('Section1', 'foo')) # -> "Python is fun!"
config.remove_option('Section1', 'bar')
config.remove_option('Section1', 'baz')
.. data:: False
- The false value of the :class:`bool` type. Assignments to ``False``
+ The false value of the :class:`bool` type. Assignments to ``False``
are illegal and raise a :exc:`SyntaxError`.
.. data:: True
- The true value of the :class:`bool` type. Assignments to ``True``
+ The true value of the :class:`bool` type. Assignments to ``True``
are illegal and raise a :exc:`SyntaxError`.
username = input('Python login:')
cryptedpasswd = pwd.getpwnam(username)[1]
if cryptedpasswd:
- if cryptedpasswd == 'x' or cryptedpasswd == '*':
+ if cryptedpasswd == 'x' or cryptedpasswd == '*':
raise "Sorry, currently no support for shadow passwords"
cleartext = getpass.getpass()
return crypt.crypt(cleartext, cryptedpasswd) == cryptedpasswd
be split into lines in a manner which preserves the newline characters.
A short usage example::
-
+
>>> import csv
>>> spamReader = csv.reader(open('eggs.csv'), delimiter=' ', quotechar='|')
>>> for row in spamReader:
considered to be true if and only if it isn't equal to ``timedelta(0)``.
Example usage:
-
+
>>> from datetime import timedelta
>>> year = timedelta(days=365)
- >>> another_year = timedelta(weeks=40, days=84, hours=23,
+ >>> another_year = timedelta(weeks=40, days=84, hours=23,
... minutes=50, seconds=600) # adds up to 365 days
>>> year == another_year
True
True
>>> my_birthday = date(today.year, 6, 24)
>>> if my_birthday < today:
- ... my_birthday = my_birthday.replace(year=today.year + 1)
+ ... my_birthday = my_birthday.replace(year=today.year + 1)
>>> my_birthday
datetime.date(2008, 6, 24)
- >>> time_to_birthday = abs(my_birthday - today)
+ >>> time_to_birthday = abs(my_birthday - today)
>>> time_to_birthday.days
202
>>> tt = dt.timetuple()
>>> for it in tt: # doctest: +SKIP
... print(it)
- ...
+ ...
2006 # year
11 # month
21 # day
... def __init__(self): # DST starts last Sunday in March
... d = datetime(dt.year, 4, 1) # ends last Sunday in October
... self.dston = d - timedelta(days=d.weekday() + 1)
- ... d = datetime(dt.year, 11, 1)
+ ... d = datetime(dt.year, 11, 1)
... self.dstoff = d - timedelta(days=d.weekday() + 1)
... def utcoffset(self, dt):
... return timedelta(hours=1) + self.dst(dt)
- ... def dst(self, dt):
+ ... def dst(self, dt):
... if self.dston <= dt.replace(tzinfo=None) < self.dstoff:
... return timedelta(hours=1)
... else:
... return timedelta(0)
... def tzname(self,dt):
... return "GMT +1"
- ...
+ ...
>>> class GMT2(tzinfo):
... def __init__(self):
- ... d = datetime(dt.year, 4, 1)
+ ... d = datetime(dt.year, 4, 1)
... self.dston = d - timedelta(days=d.weekday() + 1)
- ... d = datetime(dt.year, 11, 1)
+ ... d = datetime(dt.year, 11, 1)
... self.dstoff = d - timedelta(days=d.weekday() + 1)
... def utcoffset(self, dt):
... return timedelta(hours=1) + self.dst(dt)
... return timedelta(0)
... def tzname(self,dt):
... return "GMT +2"
- ...
+ ...
>>> gmt1 = GMT1()
>>> # Daylight Saving Time
>>> dt1 = datetime(2006, 11, 21, 16, 30, tzinfo=gmt1)
datetime.datetime(2006, 6, 14, 13, 0, tzinfo=<GMT1 object at 0x...>)
>>> dt2.utctimetuple() == dt3.utctimetuple()
True
-
+
.. _datetime-time:
return ``None`` or a string object.
Example:
-
+
>>> from datetime import time, tzinfo
>>> class GMT1(tzinfo):
... def utcoffset(self, dt):
- ... return timedelta(hours=1)
- ... def dst(self, dt):
+ ... return timedelta(hours=1)
+ ... def dst(self, dt):
... return timedelta(0)
... def tzname(self,dt):
... return "Europe/Prague"
:class:`tzinfo` subclasses; there are no ambiguities when using UTC, or any
other fixed-offset :class:`tzinfo` subclass (such as a class representing only
EST (fixed offset -5 hours), or only EDT (fixed offset -4 hours)).
-
+
.. _strftime-behavior:
The full set of format codes supported varies across platforms, because Python
calls the platform C library's :func:`strftime` function, and platform
-variations are common.
+variations are common.
The following is a list of all the format codes that the C standard (1989
version) requires, and these work on all platforms with a standard C
infinity ::= 'Infinity' | 'Inf'
nan ::= 'NaN' [digits] | 'sNaN' [digits]
numeric-value ::= decimal-part [exponent-part] | infinity
- numeric-string ::= [sign] numeric-value | [sign] nan
+ numeric-string ::= [sign] numeric-value | [sign] nan
If *value* is a :class:`tuple`, it should have three components, a sign
(:const:`0` for positive or :const:`1` for negative), a :class:`tuple` of
* :const:`ROUND_HALF_EVEN` (to nearest with ties going to nearest even integer),
* :const:`ROUND_HALF_UP` (to nearest with ties going away from zero), or
* :const:`ROUND_UP` (away from zero).
- * :const:`ROUND_05UP` (away from zero if last digit after rounding towards zero
+ * :const:`ROUND_05UP` (away from zero if last digit after rounding towards zero
would have been 0 or 5; otherwise towards zero)
The *traps* and *flags* fields list any signals to be set. Generally, new
sqrt(-x) and x > 0
0 ** 0
x ** (non-integer)
- x ** Infinity
+ x ** Infinity
.. class:: Overflow
Decimal('9.51111111')
>>> u + (v + w)
Decimal('9.51111111')
- >>>
+ >>>
>>> u, v, w = Decimal(20000), Decimal(-6), Decimal('6.0000003')
>>> (u*v) + (u*w)
Decimal('0.0060000')
"""
q = Decimal(10) ** -places # 2 places --> '0.01'
- sign, digits, exp = value.quantize(q).as_tuple()
+ sign, digits, exp = value.quantize(q).as_tuple()
result = []
digits = list(map(str, digits))
build, next = result.append, digits.pop
getcontext().prec += 2
i, lasts, s, fact, num = 0, 0, 1, 1, 1
while s != lasts:
- lasts = s
+ lasts = s
i += 1
fact *= i
- num *= x
- s += num / fact
- getcontext().prec -= 2
+ num *= x
+ s += num / fact
+ getcontext().prec -= 2
return +s
def cos(x):
getcontext().prec += 2
i, lasts, s, fact, num, sign = 0, 0, 1, 1, 1, 1
while s != lasts:
- lasts = s
+ lasts = s
i += 2
fact *= i * (i-1)
num *= x * x
sign *= -1
- s += num / fact * sign
- getcontext().prec -= 2
+ s += num / fact * sign
+ getcontext().prec -= 2
return +s
def sin(x):
getcontext().prec += 2
i, lasts, s, fact, num, sign = 1, 0, x, 1, x, 1
while s != lasts:
- lasts = s
+ lasts = s
i += 2
fact *= i * (i-1)
num *= x * x
sign *= -1
- s += num / fact * sign
- getcontext().prec -= 2
+ s += num / fact * sign
+ getcontext().prec -= 2
return +s
>>> Decimal('3.214').quantize(TWOPLACES)
Decimal('3.21')
- >>> # Validate that a number does not exceed two places
+ >>> # Validate that a number does not exceed two places
>>> Decimal('3.21').quantize(TWOPLACES, context=Context(traps=[Inexact]))
Decimal('3.21')
Detect all offsets in the code object *code* which are jump targets, and
return a list of these offsets.
-
-
+
+
.. data:: opname
Sequence of operation names, indexable using the bytecode.
The low byte of *counts* is the number of values before the list value, the
high byte of *counts* the number of values after it. The resulting values
are put onto the stack right-to-left.
-
+
.. opcode:: DUP_TOPX (count)
opcode finds the keyword parameters first. For each keyword argument, the value
is on top of the key. Below the keyword parameters, the positional parameters
are on the stack, with the right-most parameter on top. Below the parameters,
- the function object to call is on the stack. Pops all function arguments, and
+ the function object to call is on the stack. Pops all function arguments, and
the function itself off the stack, and pushes the return value.
----------------------------------------------------------
.. module:: email.mime
- :synopsis: Build MIME messages.
+ :synopsis: Build MIME messages.
Ordinarily, you get a message object structure by passing a file or some text to
when standard input is read.
.. warning::
-
+
The current implementation does not work for MS-DOS 8+3 filesystems.
the range ``0 <= x < 256``. :class:`bytes` is an immutable version of
:class:`bytearray` -- it has the same non-mutating methods and the same
indexing and slicing behavior.
-
+
Accordingly, constructor arguments are interpreted as for :func:`buffer`.
Bytes objects can also be created with literals, see :ref:`strings`.
Take two (non complex) numbers as arguments and return a pair of numbers
consisting of their quotient and remainder when using integer division. With mixed
- operand types, the rules for binary arithmetic operators apply. For integers,
+ operand types, the rules for binary arithmetic operators apply. For integers,
the result is the same as ``(a // b, a % b)``. For floating point
numbers the result is ``(q, a % b)``, where *q* is usually ``math.floor(a / b)``
but may be 1 less than that. In any case ``q * b + a % b`` is very close to
.. index::
pair: str; format
single: __format__
-
+
Convert a string or a number to a "formatted" representation, as controlled
by *format_spec*. The interpretation of *format_spec* will depend on the
type of the *value* argument, however there is a standard formatting syntax
that is used by most built-in types: :ref:`formatspec`.
-
+
.. note::
``format(value, format_spec)`` merely calls ``value.__format__(format_spec)``.
returns ``['a', 'b', 'c']`` and ``list( (1, 2, 3) )`` returns ``[1, 2, 3]``. If
no argument is given, returns a new empty list, ``[]``.
- :class:`list` is a mutable sequence type, as documented in :ref:`typesseq`.
+ :class:`list` is a mutable sequence type, as documented in :ref:`typesseq`.
.. function:: locals()
.. function:: open(file[, mode='r'[, buffering=None[, encoding=None[, errors=None[, newline=None[, closefd=True]]]]]])
Open a file. If the file cannot be opened, :exc:`IOError` is raised.
-
+
*file* is either a string or bytes object giving the name (and the path if
the file isn't in the current working directory) of the file to be opened or
an integer file descriptor of the file to be wrapped. (If a file descriptor
*buffering* is an optional integer used to set the buffering policy. By
default full buffering is on. Pass 0 to switch buffering off (only allowed in
binary mode), 1 to set line buffering, and an integer > 1 for full buffering.
-
+
*encoding* is the name of the encoding used to decode or encode the file.
This should only be used in text mode. The default encoding is platform
dependent, but any encoding supported by Python can be passed. See the
.. function:: str([object[, encoding[, errors]]])
Return a string version of an object, using one of the following modes:
-
+
If *encoding* and/or *errors* are given, :func:`str` will decode the
*object* which can either be a byte string or a character buffer using
the codec for *encoding*. The *encoding* parameter is a string giving
errors, while a value of ``'ignore'`` causes errors to be silently ignored,
and a value of ``'replace'`` causes the official Unicode replacement character,
U+FFFD, to be used to replace input characters which cannot be decoded.
- See also the :mod:`codecs` module.
+ See also the :mod:`codecs` module.
When only *object* is given, this returns its nicely printable representation.
For strings, this is the string itself. The difference with ``repr(object)``
single inheritance, :func:`super` can be used to refer to parent classes without
naming them explicitly, thus making the code more maintainable. This use
closely parallels the use of "super" in other programming languages.
-
+
The second use case is to support cooperative multiple inheritence in a
- dynamic execution environment. This use case is unique to Python and is
- not found in statically compiled languages or languages that only support
+ dynamic execution environment. This use case is unique to Python and is
+ not found in statically compiled languages or languages that only support
single inheritance. This makes in possible to implement "diamond diagrams"
where multiple base classes implement the same method. Good design dictates
that this method have the same calling signature in every case (because the
3])`` returns ``(1, 2, 3)``. If no argument is given, returns a new empty
tuple, ``()``.
- :class:`tuple` is an immutable sequence type, as documented in :ref:`typesseq`.
+ :class:`tuple` is an immutable sequence type, as documented in :ref:`typesseq`.
.. function:: type(object)
>>> class X(object):
... a = 1
- ...
+ ...
>>> X = type('X', (object,), dict(a=1))
.. function:: zip(*iterables)
- Make an iterator that aggregates elements from each of the iterables.
+ Make an iterator that aggregates elements from each of the iterables.
Returns an iterator of tuples, where the *i*-th tuple contains
the *i*-th element from each of the argument sequences or iterables. The
iterator stops when the shortest input iterable is exhausted. With a single
- iterable argument, it returns an iterator of 1-tuples. With no arguments,
+ iterable argument, it returns an iterator of 1-tuples. With no arguments,
it returns an empty iterator. Equivalent to::
def zip(*iterables):
For example, the statement ``import spam`` results in bytecode resembling the
following code::
-
+
spam = __import__('spam', globals(), locals(), [], -1)
The statement ``import spam.ham`` results in this call::
If the message id is not found in the catalog, and a fallback is specified, the
request is forwarded to the fallback's :meth:`ngettext` method. Otherwise, when
*n* is 1 *singular* is returned, and *plural* is returned in all other cases.
-
+
Here is an example::
n = len(os.listdir('.'))
H
N
-
+
The module also offers three general purpose functions based on heaps.
Keywords
orange
- Strings
+ Strings
green
Comments
.. function:: getargspec(func)
- Get the names and default values of a function's arguments. A
+ Get the names and default values of a function's arguments. A
:term:`named tuple` ``ArgSpec(args, varargs, keywords,
defaults)`` is returned. *args* is a list of
the argument names. *varargs* and *varkw* are the names of the ``*`` and
.. function:: getargvalues(frame)
- Get information about arguments passed into a particular frame. A :term:`named tuple`
+ Get information about arguments passed into a particular frame. A :term:`named tuple`
``ArgInfo(args, varargs, keywords, locals)`` is returned. *args* is a list of the
argument names (it may contain nested lists). *varargs* and *varkw* are the
names of the ``*`` and ``**`` arguments or ``None``. *locals* is the locals
.. function:: getframeinfo(frame[, context])
- Get information about a frame or traceback object. A :term:`named tuple`
+ Get information about a frame or traceback object. A :term:`named tuple`
``Traceback(filename, lineno, function, code_context, index)`` is returned.
.. method:: close()
Flush and close this stream. This method has no effect if the file is
- already closed. Once the file is closed, any operation on the file
+ already closed. Once the file is closed, any operation on the file
(e.g. reading or writing) will raise an :exc:`IOError`. The internal
file descriptor isn't closed if *closefd* was False.
.. attribute:: line_buffering
Whether line buffering is enabled.
-
+
.. class:: StringIO([initial_value[, encoding[, errors[, newline]]]])
# 'First line.\nSecond line.\n'
contents = output.getvalue()
- # Close object and discard memory buffer --
+ # Close object and discard memory buffer --
# .getvalue() will now raise an exception.
output.close()
.. function:: itertools.chain.from_iterable(iterable)
- Alternate constructor for :func:`chain`. Gets chained inputs from a
+ Alternate constructor for :func:`chain`. Gets chained inputs from a
single iterable argument that is evaluated lazily. Equivalent to::
@classmethod
Return *r* length subsequences of elements from the input *iterable*.
- Combinations are emitted in lexicographic sort order. So, if the
+ Combinations are emitted in lexicographic sort order. So, if the
input *iterable* is sorted, the combination tuples will be produced
- in sorted order.
+ in sorted order.
Elements are treated as unique based on their position, not on their
value. So if the input elements are unique, there will be no repeat
Return successive *r* length permutations of elements in the *iterable*.
If *r* is not specified or is ``None``, then *r* defaults to the length
- of the *iterable* and all possible full-length permutations
+ of the *iterable* and all possible full-length permutations
are generated.
- Permutations are emitted in lexicographic sort order. So, if the
+ Permutations are emitted in lexicographic sort order. So, if the
input *iterable* is sorted, the permutation tuples will be produced
- in sorted order.
+ in sorted order.
Elements are treated as unique based on their position, not on their
value. So if the input elements are unique, there will be no repeat
else:
return
- The code for :func:`permutations` can be also expressed as a subsequence of
+ The code for :func:`permutations` can be also expressed as a subsequence of
:func:`product`, filtered to exclude entries with repeated elements (those
from the same position in the input pool)::
>>> data = [ 1, 4,5,6, 10, 15,16,17,18, 22, 25,26,27,28]
>>> for k, g in groupby(enumerate(data), lambda t:t[0]-t[1]):
... print(map(operator.itemgetter(1), g))
- ...
+ ...
[1]
[4, 5, 6]
[10]
def unique_everseen(iterable, key=None):
"List unique elements, preserving order. Remember all elements ever seen."
# unique_everseen('AAAABBBCCDAABBB') --> A B C D
- # unique_everseen('ABBCcAD', str.lower) --> A B C D
+ # unique_everseen('ABBCcAD', str.lower) --> A B C D
seen = set()
seen_add = seen.add
if key is None:
:mod:`marshal` and :mod:`pickle` modules.
Encoding basic Python object hierarchies::
-
+
>>> import json
>>> json.dumps(['foo', {'bar': ('baz', None, 1.0, 2)}])
'["foo", {"bar": ["baz", null, 1.0, 2]}]'
>>> import json
>>> print(json.dumps({'4': 5, '6': 7}, sort_keys=True, indent=4))
{
- "4": 5,
+ "4": 5,
"6": 7
}
Decoding JSON::
-
+
>>> import json
>>> json.loads('["foo", {"bar":["baz", null, 1.0, 2]}]')
['foo', {'bar': ['baz', None, 1.0, 2]}]
Decimal('1.1')
Extending :class:`JSONEncoder`::
-
+
>>> import json
>>> class ComplexEncoder(json.JSONEncoder):
... def default(self, obj):
'[2.0, 1.0]'
>>> list(ComplexEncoder().iterencode(2 + 1j))
['[', '2.0', ', ', '1.0', ']']
-
+
.. highlight:: none
Using json.tool from the shell to validate and pretty-print::
-
+
$ echo '{"json":"obj"}' | python -mjson.tool
{
"json": "obj"
.. highlight:: python
-.. note::
+.. note::
The JSON produced by this module's default settings is a subset of
YAML, so it may be used as a serializer for that as well.
For example, to support arbitrary iterators, you could implement default
like this::
-
+
def default(self, o):
try:
iterable = iter(o)
Encode the given object, *o*, and yield each string representation as
available. For example::
-
+
for chunk in JSONEncoder().iterencode(bigobject):
mysocket.write(chunk)
>>> import locale
>>> loc = locale.getlocale() # get current locale
>>> locale.setlocale(locale.LC_ALL, 'de_DE') # use German locale; name might vary with platform
- >>> locale.strcoll('f\xe4n', 'foo') # compare a string containing an umlaut
+ >>> locale.strcoll('f\xe4n', 'foo') # compare a string containing an umlaut
>>> locale.setlocale(locale.LC_ALL, '') # use user's preferred locale
>>> locale.setlocale(locale.LC_ALL, 'C') # use default (C) locale
>>> locale.setlocale(locale.LC_ALL, loc) # restore saved locale
# that's better than losing a message completely.
box.lock()
box.add(message)
- box.flush()
+ box.flush()
box.unlock()
# Remove original message
.. function:: isnan(x)
Checks if the float *x* is a NaN (not a number). NaNs are part of the
- IEEE 754 standards. Operation like but not limited to ``inf * 0``,
+ IEEE 754 standards. Operation like but not limited to ``inf * 0``,
``inf / inf`` or any operation involving a NaN, e.g. ``nan * 1``, return
a NaN.
will be relative to the offset from the beginning of the file. *offset*
defaults to 0. *offset* must be a multiple of the PAGESIZE or
ALLOCATIONGRANULARITY.
-
+
This example shows a simple way of using :class:`mmap`::
import mmap
The module implements both the normal and wide char variants of the console I/O
api. The normal API deals only with ASCII characters and is of limited use
-for internationalized applications. The wide char API should be used where
+for internationalized applications. The wide char API should be used where
ever possible
.. _msvcrt-files:
return the keycode. The :kbd:`Control-C` keypress cannot be read with this
function.
-
+
.. function:: getwch()
Wide char variant of :func:`getch`, returning a Unicode value.
-
+
.. function:: getche()
.. function:: getwche()
Wide char variant of :func:`getche`, returning a Unicode value.
-
+
.. function:: putch(char)
Print the character *char* to the console without buffering.
-
+
.. function:: putwch(unicode_char)
Wide char variant of :func:`putch`, accepting a Unicode value.
-
+
.. function:: ungetch(char)
Cause the character *char* to be "pushed back" into the console buffer; it will
be the next character read by :func:`getch` or :func:`getche`.
-
+
.. function:: ungetwch(unicode_char)
Wide char variant of :func:`ungetch`, accepting a Unicode value.
-
+
.. _msvcrt-other:
.. warning::
Some of this package's functionality requires a functioning shared semaphore
- implementation on the host operating system. Without one, the
- :mod:`multiprocessing.synchronize` module will be disabled, and attempts to
- import it will result in an :exc:`ImportError`. See
+ implementation on the host operating system. Without one, the
+ :mod:`multiprocessing.synchronize` module will be disabled, and attempts to
+ import it will result in an :exc:`ImportError`. See
:issue:`3770` for additional information.
.. note::
>>> p = Pool(5)
>>> def f(x):
... return x*x
- ...
+ ...
>>> p.map(f, [1,2,3])
Process PoolWorker-1:
Process PoolWorker-2:
print 'module name:', __name__
print 'parent process:', os.getppid()
print 'process id:', os.getpid()
-
+
def f(name):
info('function f')
print 'hello', name
-
+
if __name__ == '__main__':
info('main line')
p = Process(target=f, args=('bob',))
.. method:: put(item[, block[, timeout]])
- Put item into the queue. If the optional argument *block* is ``True``
+ Put item into the queue. If the optional argument *block* is ``True``
(the default) and *timeout* is ``None`` (the default), block if necessary until
a free slot is available. If *timeout* is a positive number, it blocks at
most *timeout* seconds and raises the :exc:`queue.Full` exception if no
acceptable. If *block* is ``True`` and *timeout* is not ``None`` then it
specifies a timeout in seconds. If *block* is ``False`` then *timeout* is
ignored.
-
+
Note that on OS/X ``sem_timedwait`` is unsupported, so timeout arguments
for these will be ignored.
server process which is using the given address and authentication key.
.. method:: get_server()
-
+
Returns a :class:`Server` object which represents the actual server under
- the control of the Manager. The :class:`Server` object supports the
+ the control of the Manager. The :class:`Server` object supports the
:meth:`serve_forever` method::
-
+
>>> from multiprocessing.managers import BaseManager
>>> m = BaseManager(address=('', 50000), authkey='abc'))
>>> server = m.get_server()
>>> s.serve_forever()
-
+
:class:`Server` additionally have an :attr:`address` attribute.
.. method:: connect()
-
+
Connect a local manager object to a remote manager process::
-
+
>>> from multiprocessing.managers import BaseManager
>>> m = BaseManager(address='127.0.0.1', authkey='abc))
>>> m.connect()
>>> queue.get()
'hello'
-Local processes can also access that queue, using the code from above on the
+Local processes can also access that queue, using the code from above on the
client to access it remotely::
>>> from multiprocessing import Process, Queue
... super(Worker, self).__init__()
... def run(self):
... self.q.put('local hello')
- ...
+ ...
>>> queue = Queue()
>>> w = Worker(queue)
>>> w.start()
>>> class QueueManager(BaseManager): pass
- ...
+ ...
>>> QueueManager.register('get_queue', callable=lambda: queue)
>>> m = QueueManager(address=('', 50000), authkey='abracadabra')
>>> s = m.get_server()
.. literalinclude:: ../includes/mp_benchmarks.py
An example/demo of how to use the :class:`managers.SyncManager`, :class:`Process`
-and others to build a system which can distribute processes and work via a
+and others to build a system which can distribute processes and work via a
distributed queue to a "cluster" of machines on a network, accessible via SSH.
You will need to have private key authentication for all hosts configured for
this to work.
Group comp.lang.python has 59 articles, range 3742 to 3803
>>> resp, subs = s.xhdr('subject', first + '-' + last)
>>> for id, sub in subs[-10:]: print(id, sub)
- ...
+ ...
3792 Re: Removing elements from a list while iterating...
3793 Re: Who likes Info files?
3794 Emacs and doc strings
3795 a few questions about the Mac implementation
3796 Re: executable python scripts
3797 Re: executable python scripts
- 3798 Re: a few questions about the Mac implementation
+ 3798 Re: a few questions about the Mac implementation
3799 Re: PROPOSAL: A Generic Python Object Interface for Python C Modules
- 3802 Re: executable python scripts
+ 3802 Re: executable python scripts
3803 Re: \POSIX{} wait and SIGCHLD
>>> s.quit()
'205 news.cwi.nl closing connection. Goodbye.'
.. testsetup::
-
+
import operator
from operator import itemgetter
Remove the value of *a* at index *b*.
-
+
.. function:: getitem(a, b)
__getitem__(a, b)
>>> class C:
... pass
- ...
+ ...
>>> import operator
>>> obj = C()
>>> operator.isMappingType(obj)
def g(obj):
return tuple(obj[item] for item in items)
return g
-
- The items can be any type accepted by the operand's :meth:`__getitem__`
- method. Dictionaries accept any hashable value. Lists, tuples, and
+
+ The items can be any type accepted by the operand's :meth:`__getitem__`
+ method. Dictionaries accept any hashable value. Lists, tuples, and
strings accept an index or a slice:
>>> itemgetter(1)('ABCDEFG')
The keyword arguments define attributes of the new Option object. The most
important option attribute is :attr:`action`, and it largely determines which
other attributes are relevant or required. If you pass irrelevant option
-attributes, or fail to pass required ones, :mod:`optparse` raises an
+attributes, or fail to pass required ones, :mod:`optparse` raises an
:exc:`OptionError` exception explaining your mistake.
An option's *action* determines what :mod:`optparse` does when it encounters
These functions all execute a new program, replacing the current process; they
do not return. On Unix, the new executable is loaded into the current process,
and will have the same process id as the caller. Errors will be reported as
- :exc:`OSError` exceptions.
+ :exc:`OSError` exceptions.
The current process is replaced immediately. Open file objects and
descriptors are not flushed, so if there may be data buffered
used to define the environment variables for the new process (these are used
instead of the current process' environment); the functions :func:`execl`,
:func:`execlp`, :func:`execv`, and :func:`execvp` all cause the new process to
- inherit the environment of the current process.
+ inherit the environment of the current process.
Availability: Unix, Windows.
(Note that the :mod:`subprocess` module provides more powerful facilities for
spawning new processes and retrieving their results; using that module is
- preferable to using these functions. Check specially the *Replacing Older
+ preferable to using these functions. Check specially the *Replacing Older
Functions with the subprocess Module* section in that documentation page.)
If *mode* is :const:`P_NOWAIT`, this function returns the process id of the new
use ALSA, you'll have to make sure its OSS compatibility layer
is active to use ossaudiodev, but you're gonna need it for the vast
majority of Linux audio apps anyways.
-
+
Sounds like things are also complicated for other BSDs. In response
to my python-dev query, Thomas Wouters said:
-
+
> Likewise, googling shows OpenBSD also uses OSS/Free -- the commercial
> OSS installation manual tells you to remove references to OSS/Free from the
> kernel :)
-
+
but Aleksander Piotrowsk actually has an OpenBSD box, and he quotes
from its <soundcard.h>:
> * WARNING! WARNING!
> * This is an OSS (Linux) audio emulator.
> * Use the Native NetBSD API for developing new code, and this
> * only for compiling Linux programs.
-
+
There's also an ossaudio manpage on OpenBSD that explains things
further. Presumably NetBSD and OpenBSD have a different standard
audio interface. That's the great thing about standards, there are so
many to choose from ... ;-)
-
+
This probably all warrants a footnote or two, but I don't understand
things well enough right now to write it! --GPW
Robin Dunn.
PyGTK, PyQt, and wxPython, all have a modern look and feel and more
-widgets than Tkinter. In addition, there are many other GUI toolkits for
+widgets than Tkinter. In addition, there are many other GUI toolkits for
Python, both cross-platform, and platform-specific. See the `GUI Programming
<http://wiki.python.org/moin/GuiProgramming>`_ page in the Python Wiki for a
much more complete list, and also for links to documents where the
(Pdb) continue
NameError: 'spam'
> <string>(1)?()
- (Pdb)
+ (Pdb)
:file:`pdb.py` can also be invoked as a script to debug other scripts. For
example::
>>> pdb.pm()
> ./mymodule.py(3)test2()
-> print(spam)
- (Pdb)
+ (Pdb)
The module defines the following functions; each enters the debugger in a
slightly different way:
.. function:: post_mortem([traceback])
- Enter post-mortem debugging of the given *traceback* object. If no
+ Enter post-mortem debugging of the given *traceback* object. If no
*traceback* is given, it uses the one of the exception that is currently
being handled (an exception must be being handled if the default is to be
used).
fact, these methods are part of the copy protocol which implements the
:meth:`__reduce__` special method. The copy protocol provides a unified
interface for retrieving the data necessary for pickling and copying
-objects. [#]_
+objects. [#]_
Although powerful, implementing :meth:`__reduce__` directly in your classes is
error prone. For this reason, class designers should use the high-level
.. XXX Add note about how extension codes could evade our protection
- mechanism (e.g. cached classes do not invokes find_class()).
+ mechanism (e.g. cached classes do not invokes find_class()).
As our examples shows, you have to be careful with what you allow to be
unpickled. Therefore if security is a concern, you may want to consider
The Python standard library provides two different profilers:
-#. :mod:`cProfile` is recommended for most users; it's a C extension
+#. :mod:`cProfile` is recommended for most users; it's a C extension
with reasonable overhead
- that makes it suitable for profiling long-running programs.
+ that makes it suitable for profiling long-running programs.
Based on :mod:`lsprof`,
- contributed by Brett Rosen and Ted Czotter.
+ contributed by Brett Rosen and Ted Czotter.
#. :mod:`profile`, a pure Python module whose interface is imitated by
- :mod:`cProfile`. Adds significant overhead to profiled programs.
- If you're trying to extend
+ :mod:`cProfile`. Adds significant overhead to profiled programs.
+ If you're trying to extend
the profiler in some way, the task might be easier with this module.
Copyright © 1994, by InfoSeek Corporation.
that the text string in the far right column was used to sort the output. The
column headings include:
- ncalls
+ ncalls
for the number of calls,
- tottime
+ tottime
for the total time spent in the given function (and excluding time made in calls
to sub-functions),
- percall
+ percall
is the quotient of ``tottime`` divided by ``ncalls``
- cumtime
+ cumtime
is the total time spent in this and all subfunctions (from invocation till
exit). This figure is accurate *even* for recursive functions.
- percall
+ percall
is the quotient of ``cumtime`` divided by primitive calls
- filename:lineno(function)
+ filename:lineno(function)
provides the respective data of each function
When there are two numbers in the first column (for example, ``43/3``), then the
.. attribute:: xmlparser.buffer_size
- The size of the buffer used when :attr:`buffer_text` is true.
- A new buffer size can be set by assigning a new integer value
- to this attribute.
+ The size of the buffer used when :attr:`buffer_text` is true.
+ A new buffer size can be set by assigning a new integer value
+ to this attribute.
When the size is changed, the buffer will be flushed.
-------------
Queue objects (:class:`Queue`, :class:`LifoQueue`, or :class:`PriorityQueue`)
-provide the public methods described below.
+provide the public methods described below.
.. method:: Queue.qsize()
Example of how to wait for enqueued tasks to be completed::
- def worker():
- while True:
- item = q.get()
- do_work(item)
- q.task_done()
+ def worker():
+ while True:
+ item = q.get()
+ do_work(item)
+ q.task_done()
- q = Queue()
- for i in range(num_worker_threads):
+ q = Queue()
+ for i in range(num_worker_threads):
t = Thread(target=worker)
t.set_daemon(True)
- t.start()
+ t.start()
for item in source():
- q.put(item)
+ q.put(item)
q.join() # block until all tasks are done
``'s'``, ``'u'``, ``'x'``.) The group matches the empty string; the
letters set the corresponding flags: :const:`re.a` (ASCII-only matching),
:const:`re.I` (ignore case), :const:`re.L` (locale dependent),
- :const:`re.M` (multi-line), :const:`re.S` (dot matches all),
+ :const:`re.M` (multi-line), :const:`re.S` (dot matches all),
and :const:`re.X` (verbose), for the entire regular expression. (The
flags are described in :ref:`contents-of-module-re`.) This
is useful if you wish to include the flags as part of the regular
counterpart ``(?u)``), but these are redundant in Python 3.0 since
matches are Unicode by default for strings (and Unicode matching
isn't allowed for bytes).
-
+
.. data:: I
IGNORECASE
>>> pair.match("717ak").group(1)
'7'
-
+
# Error because re.match() returns None, which doesn't have a group() method:
>>> pair.match("718ak").group(1)
Traceback (most recent call last):
File "<pyshell#23>", line 1, in <module>
re.match(r".*(.).*\1", "718ak").group(1)
AttributeError: 'NoneType' object has no attribute 'group'
-
+
>>> pair.match("354aa").group(1)
'a'
Making a Phonebook
^^^^^^^^^^^^^^^^^^
-:func:`split` splits a string into a list delimited by the passed pattern. The
+:func:`split` splits a string into a list delimited by the passed pattern. The
method is invaluable for converting textual data into data structures that can be
easily read and modified by Python as demonstrated in the following example that
creates a phonebook.
triple-quoted string syntax:
>>> input = """Ross McFluff: 834.345.1254 155 Elm Street
- ...
+ ...
... Ronald Heathmore: 892.345.3428 436 Finley Avenue
... Frank Burger: 925.541.7625 662 South Dogwood Way
...
If called for a dotted name, it will try to evaluate anything without obvious
side-effects (functions will not be evaluated, but it can generate calls to
:meth:`__getattr__`) up to the last part, and find matches for the rest via the
- :func:`dir` function. Any exception raised during the evaluation of the
+ :func:`dir` function. Any exception raised during the evaluation of the
expression is caught, silenced and :const:`None` is returned.
930343700.276
In multi-threaded environments, the :class:`scheduler` class has limitations
-with respect to thread-safety, inability to insert a new task before
+with respect to thread-safety, inability to insert a new task before
the one currently pending in a running scheduler, and holding up the main
thread until the event queue is empty. Instead, the preferred approach
is to use the :class:`threading.Timer` class instead.
Even the higher-level file copying functions (:func:`copy`, :func:`copy2`)
can't copy all file metadata.
-
+
On POSIX platforms, this means that file owner and group are lost as well
as ACLs. On Mac OS, the resource fork and other metadata are not used.
This means that resources will be lost and file type and creator codes will
* Some care must be taken if both signals and threads are used in the same
program. The fundamental thing to remember in using signals and threads
simultaneously is: always perform :func:`signal` operations in the main thread
- of execution. Any thread can perform an :func:`alarm`, :func:`getsignal`,
- :func:`pause`, :func:`setitimer` or :func:`getitimer`; only the main thread
- can set a new signal handler, and the main thread will be the only one to
- receive signals (this is enforced by the Python :mod:`signal` module, even
- if the underlying thread implementation supports sending signals to
- individual threads). This means that signals can't be used as a means of
+ of execution. Any thread can perform an :func:`alarm`, :func:`getsignal`,
+ :func:`pause`, :func:`setitimer` or :func:`getitimer`; only the main thread
+ can set a new signal handler, and the main thread will be the only one to
+ receive signals (this is enforced by the Python :mod:`signal` module, even
+ if the underlying thread implementation supports sending signals to
+ individual threads). This means that signals can't be used as a means of
inter-thread communication. Use locks instead.
The variables defined in the :mod:`signal` module are:
One more than the number of the highest signal number.
-.. data:: ITIMER_REAL
+.. data:: ITIMER_REAL
Decrements interval timer in real time, and delivers :const:`SIGALRM` upon expiration.
-.. data:: ITIMER_VIRTUAL
+.. data:: ITIMER_VIRTUAL
- Decrements interval timer only when the process is executing, and delivers
+ Decrements interval timer only when the process is executing, and delivers
SIGVTALRM upon expiration.
.. data:: ITIMER_PROF
-
- Decrements interval timer both when the process executes and when the
- system is executing on behalf of the process. Coupled with ITIMER_VIRTUAL,
- this timer is usually used to profile the time spent by the application
+
+ Decrements interval timer both when the process executes and when the
+ system is executing on behalf of the process. Coupled with ITIMER_VIRTUAL,
+ this timer is usually used to profile the time spent by the application
in user and kernel space. SIGPROF is delivered upon expiration.
Raised to signal an error from the underlying :func:`setitimer` or
:func:`getitimer` implementation. Expect this error if an invalid
- interval timer or a negative time is passed to :func:`setitimer`.
+ interval timer or a negative time is passed to :func:`setitimer`.
This error is a subtype of :exc:`IOError`.
.. function:: setitimer(which, seconds[, interval])
- Sets given interval timer (one of :const:`signal.ITIMER_REAL`,
+ Sets given interval timer (one of :const:`signal.ITIMER_REAL`,
:const:`signal.ITIMER_VIRTUAL` or :const:`signal.ITIMER_PROF`) specified
- by *which* to fire after *seconds* (float is accepted, different from
+ by *which* to fire after *seconds* (float is accepted, different from
:func:`alarm`) and after that every *interval* seconds. The interval
timer specified by *which* can be cleared by setting seconds to zero.
When an interval timer fires, a signal is sent to the process.
- The signal sent is dependent on the timer being used;
- :const:`signal.ITIMER_REAL` will deliver :const:`SIGALRM`,
+ The signal sent is dependent on the timer being used;
+ :const:`signal.ITIMER_REAL` will deliver :const:`SIGALRM`,
:const:`signal.ITIMER_VIRTUAL` sends :const:`SIGVTALRM`,
and :const:`signal.ITIMER_PROF` will deliver :const:`SIGPROF`.
The old values are returned as a tuple: (delay, interval).
- Attempting to pass an invalid interval timer will cause a
+ Attempting to pass an invalid interval timer will cause a
:exc:`ItimerError`.
will be restarted when interrupted by signal *signalnum*, otherwise system calls will
be interrupted. Returns nothing. Availability: Unix (see the man page
:manpage:`siginterrupt(3)` for further information).
-
+
Note that installing a signal handler with :func:`signal` will reset the restart
behaviour to interruptible by implicitly calling :cfunc:`siginterrupt` with a true *flag*
value for the given signal.
signal.alarm(5)
# This open() may hang indefinitely
- fd = os.open('/dev/ttyS0', os.O_RDWR)
+ fd = os.open('/dev/ttyS0', os.O_RDWR)
signal.alarm(0) # Disable the alarm
Identify yourself to an ESMTP server using ``EHLO``. The hostname argument
defaults to the fully qualified domain name of the local host. Examine the
- response for ESMTP option and store them for use by :meth:`has_extn`.
- Also sets several informational attributes: the message returned by
- the server is stored as the :attr:`ehlo_resp` attribute, :attr:`does_esmtp`
+ response for ESMTP option and store them for use by :meth:`has_extn`.
+ Also sets several informational attributes: the message returned by
+ the server is stored as the :attr:`ehlo_resp` attribute, :attr:`does_esmtp`
is set to true or false depending on whether the server supports ESMTP, and
:attr:`esmtp_features` will be a dictionary containing the names of the
SMTP service extensions this server supports, and their
.. data:: SIO_*
RCVALL_*
-
+
Constants for Windows' WSAIoctl(). The constants are used as arguments to the
:meth:`ioctl` method of socket objects.
-
+
.. data:: TIPC_*
all the necessary arguments for creating the corresponding socket. *host* is a domain
name, a string representation of an IPv4/v6 address or ``None``. *port* is a string
service name such as ``'http'``, a numeric port number or ``None``.
- The rest of the arguments are optional and must be numeric if specified.
+ The rest of the arguments are optional and must be numeric if specified.
By passing ``None`` as the value of *host* and *port*, , you can pass ``NULL`` to the C API.
The :func:`getaddrinfo` function returns a list of 5-tuples with the following
contents of the buffer (see the optional built-in module :mod:`struct` for a way
to decode C structures encoded as byte strings).
-
+
.. method:: socket.ioctl(control, option)
- :platform: Windows
-
+ :platform: Windows
+
The :meth:`ioctl` method is a limited interface to the WSAIoctl system
interface. Please refer to the MSDN documentation for more information.
-
+
.. method:: socket.listen(backlog)
s.close()
print('Received', repr(data))
-
+
The last example shows how to write a very simple network sniffer with raw
sockets on Windows. The example requires administrator privileges to modify
the interface::
# the public network interface
HOST = socket.gethostbyname(socket.gethostname())
-
+
# create a raw socket and bind it to the public interface
s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_IP)
s.bind((HOST, 0))
-
+
# Include IP headers
s.setsockopt(socket.IPPROTO_IP, socket.IP_HDRINCL, 1)
-
+
# receive all packages
s.ioctl(socket.SIO_RCVALL, socket.RCVALL_ON)
-
+
# receive a package
print(s.recvfrom(65565))
-
+
# disabled promiscuous mode
s.ioctl(socket.SIO_RCVALL, socket.RCVALL_OFF)
This read-only attribute provides the column names of the last query. To
remain compatible with the Python DB API, it returns a 7-tuple for each
- column where the last six items of each tuple are :const:`None`.
-
+ column where the last six items of each tuple are :const:`None`.
+
It is set for ``SELECT`` statements without any matching rows as well.
.. _sqlite3-row-objects:
.. class:: Row
A :class:`Row` instance serves as a highly optimized
- :attr:`~Connection.row_factory` for :class:`Connection` objects.
+ :attr:`~Connection.row_factory` for :class:`Connection` objects.
It tries to mimic a tuple in most of its features.
It supports mapping access by column name and index, iteration,
If two :class:`Row` objects have exactly the same columns and their
members are equal, they compare equal.
-
+
.. versionchanged:: 2.6
Added iteration and equality (hashability).
------------------------
By default, the :mod:`sqlite3` module opens transactions implicitly before a
-Data Modification Language (DML) statement (i.e.
+Data Modification Language (DML) statement (i.e.
``INSERT``/``UPDATE``/``DELETE``/``REPLACE``), and commits transactions
implicitly before a non-DML, non-query statement (i. e.
anything other than ``SELECT`` or the aforementioned).
.. exception:: SSLError
- Raised to signal an error from the underlying SSL implementation. This
+ Raised to signal an error from the underlying SSL implementation. This
signifies some problem in the higher-level
encryption and authentication layer that's superimposed on the underlying
network connection. This error is a subtype of :exc:`socket.error`, which
>>> import time
>>> time.ctime(ssl.cert_time_to_seconds("May 9 00:00:00 2007 GMT"))
'Wed May 9 00:00:00 2007'
- >>>
+ >>>
.. function:: get_server_certificate (addr, ssl_version=PROTOCOL_SSLv3, ca_certs=None)
the client or server, and then the certificate for the issuer of that
certificate, and then the certificate for the issuer of *that* certificate,
and so on up the chain till you get to a certificate which is *self-signed*,
-that is, a certificate which has the same subject and issuer,
+that is, a certificate which has the same subject and issuer,
sometimes called a *root certificate*. The certificates should just
be concatenated together in the certificate file. For example, suppose
we had a three certificate chain, from our server certificate to the
you only need the root certificates, and the remote peer is supposed to
furnish the other certificates necessary to chain from its certificate to
a root certificate.
-See :rfc:`4158` for more discussion of the way in which
+See :rfc:`4158` for more discussion of the way in which
certification chains can be built.
If you are going to create a server that provides SSL-encrypted
connection services, you will need to acquire a certificate for that
service. There are many ways of acquiring appropriate certificates,
-such as buying one from a certification authority. Another common
+such as buying one from a certification authority. Another common
practice is to generate a self-signed certificate. The simplest
way to do this is with the OpenSSL package, using something like
the following::
And go back to listening for new client connections.
-
+
.. seealso::
Class :class:`socket.socket`
any operand is a complex number, the objects are of different types that cannot
be compared, or other cases where there is no defined ordering.
-.. index::
+.. index::
single: __eq__() (instance method)
single: __ne__() (instance method)
single: __lt__() (instance method)
for well-defined conversions.
(4)
- float also accepts the strings "nan" and "inf" with an optional prefix "+"
+ float also accepts the strings "nan" and "inf" with an optional prefix "+"
or "-" for Not a Number (NaN) and positive or negative infinity.
(5)
Python defines ``pow(0, 0)`` and ``0 ** 0`` to be ``1``, as is common for
programming languages.
-
+
All :class:`numbers.Real` types (:class:`int` and
:class:`float`) also include the following operations:
original float and with a positive denominator. Raises
:exc:`OverflowError` on infinities and a :exc:`ValueError` on
NaNs.
-
+
.. versionadded:: 2.6
Two methods support conversion to
otherwise. Decimal characters include digit characters, and all characters
that that can be used to form decimal-radix numbers, e.g. U+0660,
ARABIC-INDIC DIGIT ZERO.
-
+
.. method:: str.isdigit()
that have the Unicode numeric value property, e.g. U+2155,
VULGAR FRACTION ONE FIFTH.
-
+
.. method:: str.isprintable()
Return true if all characters in the string are printable or the string is
example, sort by department, then by salary grade).
While a list is being sorted, the effect of attempting to mutate, or even
- inspect, the list is undefined. The C implementation
+ inspect, the list is undefined. The C implementation
makes the list appear empty for the duration, and raises :exc:`ValueError` if it
can detect that the list has been mutated during a sort.
b'\xf0\xf1\xf2'
The translate method differs in semantics from the version available on strings:
-
+
.. method:: bytes.translate(table[, delete])
Return a copy of the bytes or bytearray object where all bytes occurring in
Return the item of *d* with key *key*. Raises a :exc:`KeyError` if *key* is
not in the map.
-
+
If a subclass of dict defines a method :meth:`__missing__`, if the key *key*
is not present, the ``d[key]`` operation calls that method with the key *key*
as argument. The ``d[key]`` operation then returns or raises whatever is
positioning); other values are ``os.SEEK_CUR`` or ``1`` (seek relative to the
current position) and ``os.SEEK_END`` or ``2`` (seek relative to the file's
end). There is no return value.
-
+
For example, ``f.seek(2, os.SEEK_CUR)`` advances the position by two and
``f.seek(-3, os.SEEK_END)`` sets the position to the third to last.
:meth:`format` is just a wrapper that calls :meth:`vformat`.
.. method:: vformat(format_string, args, kwargs)
-
+
This function does the actual work of formatting. It is exposed as a
separate function for cases where you want to pass in a predefined
dictionary of arguments, rather than unpacking and repacking the
intended to be replaced by subclasses:
.. method:: parse(format_string)
-
+
Loop over the format_string and return an iterable of tuples
(*literal_text*, *field_name*, *format_spec*, *conversion*). This is used
by :meth:`vformat` to break the string in to either literal text, or
replacement fields.
-
+
The values in the tuple conceptually represent a span of literal text
followed by a single replacement field. If there is no literal text
(which can happen if two replacement fields occur consecutively), then
*key* parameter to :meth:`get_value`.
.. method:: get_value(key, args, kwargs)
-
+
Retrieve a given field value. The *key* argument will be either an
integer or a string. If it is an integer, it represents the index of the
positional argument in *args*; if it is a string, then it represents a
method is provided so that subclasses can override it.
.. method:: convert_field(value, conversion)
-
+
Converts the value (returned by :meth:`get_field`) given a conversion type
(as in the tuple returned by the :meth:`parse` method.) The default
version understands 'r' (repr) and 's' (str) conversion types.
element_index: `integer`
conversion: "r" | "s" | "a"
format_spec: <described in the next section>
-
+
In less formal terms, the replacement field starts with a *field_name*, which
can either be a number (for a positional argument), or an identifier (for
keyword arguments). Following this is an optional *conversion* field, which is
"My quest is {name}" # References keyword argument 'name'
"Weight in tons {0.weight}" # 'weight' attribute of first positional arg
"Units destroyed: {players[0]}" # First element of keyword argument 'players'.
-
+
The *conversion* field causes a type coercion before formatting. Normally, the
job of formatting a value is done by the :meth:`__format__` method of the value
itself. However, in some cases it is desirable to force a type to be formatted
Then the outer replacement field would be evaluated, producing::
"noses "
-
+
Which is substituted into the string, yielding::
-
+
"A man with two noses "
-
+
(The extra space is because we specified a field width of 10, and because left
alignment is the default for strings.)
width: `integer`
precision: `integer`
type: "b" | "c" | "d" | "e" | "E" | "f" | "F" | "g" | "G" | "n" | "o" | "x" | "X" | "%"
-
+
The *fill* character can be any character other than '}' (which signifies the
end of the field). The presence of a fill character is signaled by the *next*
character, which must be one of the alignment options. If the second character
+---------+----------------------------------------------------------+
| None | The same as ``'d'``. |
+---------+----------------------------------------------------------+
-
+
The available presentation types for floating point and decimal values are:
-
+
+---------+----------------------------------------------------------+
| Type | Meaning |
+=========+==========================================================+
Special value that can be used as the *stderr* argument to :class:`Popen` and
indicates that standard error should go into the same handle as standard
output.
-
+
Convenience Functions
^^^^^^^^^^^^^^^^^^^^^
The child return code, set by :meth:`poll` and :meth:`wait` (and indirectly
by :meth:`communicate`). A ``None`` value indicates that the process
hasn't terminated yet.
-
+
A negative value ``-N`` indicates that the child was terminated by signal
``N`` (Unix only).
The *default* argument allows to define a value which will be returned
if the object type does not provide means to retrieve the size and would
- cause a `TypeError`.
+ cause a `TypeError`.
func:`getsizeof` calls the object's __sizeof__ method and adds an additional
garbage collector overhead if the object is managed by the garbage collector.
The events have the following meaning:
- ``'call'``
+ ``'call'``
A function is called (or some other code block entered). The
global trace function is called; *arg* is ``None``; the return value
specifies the local trace function.
prompts of :func:`input`. The interpreter's own prompts
and (almost all of) its error messages go to ``stderr``. ``stdout`` and
``stderr`` needn't be built-in file objects: any object is acceptable as long
- as it has a :meth:`write` method that takes a string argument. (Changing these
+ as it has a :meth:`write` method that takes a string argument. (Changing these
objects doesn't affect the standard I/O streams of processes executed by
:func:`os.popen`, :func:`os.system` or the :func:`exec\*` family of functions in
the :mod:`os` module.)
Tk/Tcl has long been an integral part of Python. It provides a robust and
platform independent windowing toolkit, that is available to Python programmers
-using the :mod:`tkinter` package, and its extension, the :mod:`tkinter.tix`
+using the :mod:`tkinter` package, and its extension, the :mod:`tkinter.tix`
module.
The :mod:`tkinter` package is a thin object-oriented layer on top of Tcl/Tk. To
mechanism which allows Python and Tcl to interact.
:mod:`tkinter`'s chief virtues are that it is fast, and that it usually comes
-bundled with Python. Although its standard documentation is weak, good
-material is available, which includes: references, tutorials, a book and
-others. :mod:`tkinter` is also famous for having an outdated look and feel,
-which has been vastly improved in Tk 8.5. Nevertheless, there are many other
-GUI libraries that you could be interested in. For more information about
+bundled with Python. Although its standard documentation is weak, good
+material is available, which includes: references, tutorials, a book and
+others. :mod:`tkinter` is also famous for having an outdated look and feel,
+which has been vastly improved in Tk 8.5. Nevertheless, there are many other
+GUI libraries that you could be interested in. For more information about
alternatives, see the :ref:`other-gui-packages` section.
.. toctree::
-
+
tkinter.rst
tkinter.tix.rst
tkinter.scrolledtext.rst
linked with the Python interpreter.
In addition to the Tk interface module, :mod:`tkinter` includes a number of
-Python modules, :mod:`tkinter.constants` being one of the most important.
+Python modules, :mod:`tkinter.constants` being one of the most important.
Importing :mod:`tkinter` will automatically import :mod:`tkinter.constants`,
so, usually, to use Tkinter all you need is a simple import statement::
Basic dialogs and convenience functions.
:mod:`tkinter.dnd`
- Drag-and-drop support for :mod:`tkinter`. This is experimental and should
+ Drag-and-drop support for :mod:`tkinter`. This is experimental and should
become deprecated when it is replaced with the Tk DND.
:mod:`turtle`
the novice. The book is not exhaustive, and for many details it defers to the
man pages.
-* :file:`tkinter/__init__.py` is a last resort for most, but can be a good
+* :file:`tkinter/__init__.py` is a last resort for most, but can be a good
place to go when nothing else makes sense.
someOptions), in C++, you would express this as fred.someAction(someOptions),
and in Tk, you say::
- .fred someAction someOptions
+ .fred someAction someOptions
Note that the object name, ``.fred``, starts with a dot.
arguments. In Tkinter, the Pack class holds all this functionality, and the
various forms of the pack command are implemented as methods. All widgets in
:mod:`tkinter` are subclassed from the Packer, and so inherit all the packing
-methods. See the :mod:`tkinter.tix` module documentation for additional
+methods. See the :mod:`tkinter.tix` module documentation for additional
information on the Form geometry manager. ::
pack .fred -side left =====> fred.pack(side = "left")
For more extensive information on the packer and the options that it can take,
see the man pages and page 183 of John Ousterhout's book.
-anchor
+anchor
Anchor type. Denotes where the packer is to place each slave in its parcel.
expand
they are denoted in Tk, which can be useful when referring to the Tk man pages.
::
- Tk Tkinter Event Field Tk Tkinter Event Field
+ Tk Tkinter Event Field Tk Tkinter Event Field
-- ------------------- -- -------------------
%f focus %A char
%h height %E send_event
.. index:: single: Tix
-The :mod:`tkinter.tix` (Tk Interface Extension) module provides an additional
-rich set of widgets. Although the standard Tk library has many useful widgets,
+The :mod:`tkinter.tix` (Tk Interface Extension) module provides an additional
+rich set of widgets. Although the standard Tk library has many useful widgets,
they are far from complete. The :mod:`tkinter.tix` library provides most of the
-commonly needed widgets that are missing from standard Tk: :class:`HList`,
-:class:`ComboBox`, :class:`Control` (a.k.a. SpinBox) and an assortment of
-scrollable widgets.
+commonly needed widgets that are missing from standard Tk: :class:`HList`,
+:class:`ComboBox`, :class:`Control` (a.k.a. SpinBox) and an assortment of
+scrollable widgets.
:mod:`tkinter.tix` also includes many more widgets that are generally useful in
a wide range of applications: :class:`NoteBook`, :class:`FileEntry`,
:class:`PanedWindow`, etc; there are more than 40 of them.
Toplevel widget of Tix which represents mostly the main window of an
application. It has an associated Tcl interpreter.
- Classes in the :mod:`tkinter.tix` module subclasses the classes in the
- :mod:`tkinter`. The former imports the latter, so to use :mod:`tkinter.tix`
- with Tkinter, all you need to do is to import one module. In general, you
- can just import :mod:`tkinter.tix`, and replace the toplevel call to
+ Classes in the :mod:`tkinter.tix` module subclasses the classes in the
+ :mod:`tkinter`. The former imports the latter, so to use :mod:`tkinter.tix`
+ with Tkinter, all you need to do is to import one module. In general, you
+ can just import :mod:`tkinter.tix`, and replace the toplevel call to
:class:`tkinter.Tk` with :class:`tix.Tk`::
from tkinter import tix
The :mod:`tkinter.tix` module adds:
* `pixmap <http://tix.sourceforge.net/dist/current/man/html/TixCmd/pixmap.htm>`_
- capabilities to all :mod:`tkinter.tix` and :mod:`tkinter` widgets to create
+ capabilities to all :mod:`tkinter.tix` and :mod:`tkinter` widgets to create
color images from XPM files.
.. Python Demo of:
The :func:`tokenize` generator requires one argument, *readline*, which
must be a callable object which provides the same interface as the
:meth:`readline` method of built-in file objects (see section
- :ref:`bltin-file-objects`). Each call to the function should return one
+ :ref:`bltin-file-objects`). Each call to the function should return one
line of input as bytes.
- The generator produces 5-tuples with these members: the token type; the
- token string; a 2-tuple ``(srow, scol)`` of ints specifying the row and
- column where the token begins in the source; a 2-tuple ``(erow, ecol)`` of
- ints specifying the row and column where the token ends in the source; and
+ The generator produces 5-tuples with these members: the token type; the
+ token string; a 2-tuple ``(srow, scol)`` of ints specifying the row and
+ column where the token begins in the source; a 2-tuple ``(erow, ecol)`` of
+ ints specifying the row and column where the token ends in the source; and
the line on which the token was found. The line passed (the last tuple item)
is the *logical* line; continuation lines are included.
-
+
:func:`tokenize` determines the source encoding of the file by looking for a
UTF-8 BOM or encoding cookie, according to :pep:`263`.
.. data:: NL
Token value used to indicate a non-terminating newline. The NEWLINE token
- indicates the end of a logical line of Python code; NL tokens are generated
+ indicates the end of a logical line of Python code; NL tokens are generated
when a logical line of code is continued over multiple physical lines.
.. data:: ENCODING
- Token value that indicates the encoding used to decode the source bytes
- into text. The first token returned by :func:`tokenize` will always be an
+ Token value that indicates the encoding used to decode the source bytes
+ into text. The first token returned by :func:`tokenize` will always be an
ENCODING token.
-Another function is provided to reverse the tokenization process. This is
-useful for creating tools that tokenize a script, modify the token stream, and
+Another function is provided to reverse the tokenization process. This is
+useful for creating tools that tokenize a script, modify the token stream, and
write back the modified script.
.. function:: untokenize(iterable)
Converts tokens back into Python source code. The *iterable* must return
- sequences with at least two elements, the token type and the token string.
+ sequences with at least two elements, the token type and the token string.
Any additional sequence elements are ignored.
-
+
The reconstructed script is returned as a single string. The result is
guaranteed to tokenize back to match the input so that the conversion is
- lossless and round-trips are assured. The guarantee applies only to the
- token type and token string as the spacing between tokens (column
+ lossless and round-trips are assured. The guarantee applies only to the
+ token type and token string as the spacing between tokens (column
positions) may change.
-
- It returns bytes, encoded using the ENCODING token, which is the first
+
+ It returns bytes, encoded using the ENCODING token, which is the first
token sequence output by :func:`tokenize`.
.. function:: detect_encoding(readline)
- The :func:`detect_encoding` function is used to detect the encoding that
- should be used to decode a Python source file. It requires one argment,
+ The :func:`detect_encoding` function is used to detect the encoding that
+ should be used to decode a Python source file. It requires one argment,
readline, in the same way as the :func:`tokenize` generator.
-
+
It will call readline a maximum of twice, and return the encoding used
(as a string) and a list of any lines (not decoded from bytes) it has read
in.
-
+
It detects the encoding from the presence of a utf-8 bom or an encoding
cookie as specified in pep-0263. If both a bom and a cookie are present,
but disagree, a SyntaxError will be raised.
-
- If no encoding is specified, then the default of 'utf-8' will be returned.
-
+ If no encoding is specified, then the default of 'utf-8' will be returned.
+
+
Example of a script re-writer that transforms float literals into Decimal
objects::
def decistmt(s):
"""Substitute Decimals for floats in a string of statements.
-
+
>>> from decimal import Decimal
>>> s = 'print(+21.3e-5*-.1234/81.7)'
>>> decistmt(s)
"print (+Decimal ('21.3e-5')*-Decimal ('.1234')/Decimal ('81.7'))"
-
+
The format of the exponent is inherited from the platform C library.
Known cases are "e-007" (Windows) and "e-07" (not Windows). Since
we're only showing 12 digits, and the 13th isn't close to 5, the
rest of the output should be platform-independent.
-
+
>>> exec(s) #doctest: +ELLIPSIS
-3.21716034272e-0...7
-
+
Output from calculations with Decimal should be identical across all
platforms.
-
+
>>> exec(decistmt(s))
-3.217160342717258261933904529E-7
"""
:option:`--ignore-module`
Accepts comma separated list of module names. Ignore each of the named
- module and its submodules (if it is a package). May be given
+ module and its submodules (if it is a package). May be given
multiple times.
:option:`--ignore-dir`
Ignore all modules and packages in the named directory and subdirectories
(multiple directories can be joined by os.pathsep). May be given multiple
- times.
+ times.
.. _trace-api:
def lumberjack():
bright_side_of_death()
-
+
def bright_side_of_death():
return tuple()[0]
-
+
try:
lumberjack()
except:
>>> import traceback
>>> def another_function():
... lumberstack()
- ...
+ ...
>>> def lumberstack():
... traceback.print_stack()
... print(repr(traceback.extract_stack()))
... print(repr(traceback.format_stack()))
- ...
+ ...
>>> another_function()
File "<doctest>", line 10, in <module>
another_function()
Subclass of TurtleScreen, with :ref:`four methods added <screenspecific>`.
-
+
.. class:: ScrolledCavas(master)
:param master: some Tkinter widget to contain the ScrolledCanvas, i.e.
"compound" ``None`` (a compund shape has to be constructed using the
:meth:`addcomponent` method)
=========== ===========
-
+
.. method:: addcomponent(poly, fill, outline=None)
:param poly: a polygon, i.e. a tuple of pairs of numbers
:param fill: a color the *poly* will be filled with
:param outline: a color for the poly's outline (if given)
-
+
Example:
>>> poly = ((0,0),(10,-5),(0,10),(-10,-5))
>>> help(Screen.bgcolor)
Help on method bgcolor in module turtle:
-
+
bgcolor(self, *args) unbound turtle.Screen method
Set or return backgroundcolor of the TurtleScreen.
-
+
Arguments (if given): a color string or three numbers
in the range 0..colormode or a 3-tuple of such numbers.
-
-
+
+
>>> screen.bgcolor("orange")
>>> screen.bgcolor()
"orange"
>>> screen.bgcolor(0.5,0,0.5)
>>> screen.bgcolor()
"#800080"
-
+
>>> help(Turtle.penup)
Help on method penup in module turtle:
-
+
penup(self) unbound turtle.Turtle method
Pull the pen up -- no drawing when moving.
-
+
Aliases: penup | pu | up
-
+
No argument
-
+
>>> turtle.penup()
- The docstrings of the functions which are derived from methods have a modified
>>> help(bgcolor)
Help on function bgcolor in module turtle:
-
+
bgcolor(*args)
Set or return backgroundcolor of the TurtleScreen.
-
+
Arguments (if given): a color string or three numbers
in the range 0..colormode or a 3-tuple of such numbers.
-
+
Example::
-
+
>>> bgcolor("orange")
>>> bgcolor()
"orange"
>>> bgcolor(0.5,0,0.5)
>>> bgcolor()
"#800080"
-
+
>>> help(penup)
Help on function penup in module turtle:
-
+
penup()
Pull the pen up -- no drawing when moving.
-
+
Aliases: penup | pu | up
-
+
No argument
-
+
Example:
>>> penup()
Changes since Python 2.6
========================
-- The methods :meth:`Turtle.tracer`, :meth:`Turtle.window_width` and
- :meth:`Turtle.window_height` have been eliminated.
- Methods with these names and functionality are now available only
+- The methods :meth:`Turtle.tracer`, :meth:`Turtle.window_width` and
+ :meth:`Turtle.window_height` have been eliminated.
+ Methods with these names and functionality are now available only
as methods of :class:`Screen`. The functions derived from these remain
- available. (In fact already in Python 2.6 these methods were merely
- duplications of the corresponding
+ available. (In fact already in Python 2.6 these methods were merely
+ duplications of the corresponding
:class:`TurtleScreen`/:class:`Screen`-methods.)
-- The method :meth:`Turtle.fill` has been eliminated.
- The behaviour of :meth:`begin_fill` and :meth:`end_fill`
- have changed slightly: now every filling-process must be completed with an
+- The method :meth:`Turtle.fill` has been eliminated.
+ The behaviour of :meth:`begin_fill` and :meth:`end_fill`
+ have changed slightly: now every filling-process must be completed with an
``end_fill()`` call.
-
+
- A method :meth:`Turtle.filling` has been added. It returns a boolean
value: ``True`` if a filling process is under way, ``False`` otherwise.
This behaviour corresponds to a ``fill()`` call without arguments in
File "<stdin>", line 1, in ?
ValueError: not a decimal
>>> unicodedata.category('A') # 'L'etter, 'u'ppercase
- 'Lu'
+ 'Lu'
>>> unicodedata.bidirectional('\u0660') # 'A'rabic, 'N'umber
'AN'
TestCase.failUnlessAlmostEqual(first, second[, places[, msg]])
Test that *first* and *second* are approximately equal by computing the
- difference, rounding to the given number of decimal *places* (default 7),
+ difference, rounding to the given number of decimal *places* (default 7),
and comparing to zero.
Note that comparing a given number of decimal places is not the same as
comparing a given number of significant digits. If the values do not compare
TestCase.failIfAlmostEqual(first, second[, places[, msg]])
Test that *first* and *second* are not approximately equal by computing the
- difference, rounding to the given number of decimal *places* (default 7),
+ difference, rounding to the given number of decimal *places* (default 7),
and comparing to zero.
Note that comparing a given number of decimal places is not the same as
comparing a given number of significant digits. If the values do not compare
this function with an alternative implementation by assigning to
``warnings.showwarning``.
*line* is a line of source code to be included in the warning
- message; if *line* is not supplied, :func:`showwarning` will
+ message; if *line* is not supplied, :func:`showwarning` will
try to read the line specified by *filename* and *lineno*.
.. function:: formatwarning(message, category, filename, lineno[, line])
Format a warning the standard way. This returns a string which may contain
- embedded newlines and ends in a newline. *line* is
- a line of source code to be included in the warning message; if *line* is not supplied,
+ embedded newlines and ends in a newline. *line* is
+ a line of source code to be included in the warning message; if *line* is not supplied,
:func:`formatwarning` will try to read the line specified by *filename* and *lineno*.
url = 'http://www.python.org'
- # Open URL in a new tab, if a browser window is already open.
+ # Open URL in a new tab, if a browser window is already open.
webbrowser.open_new_tab(url + '/doc')
# Open URL in new window, raising the window if possible.
filelike = StringIO("This is an example file-like object"*10)
wrapper = FileWrapper(filelike, blksize=5)
- for chunk in wrapper:
+ for chunk in wrapper:
print(chunk)
from wsgiref.validate import validator
from wsgiref.simple_server import make_server
- # Our callable object which is intentionally not compliant to the
+ # Our callable object which is intentionally not compliant to the
# standard, so the validator is going to break
def simple_app(environ, start_response):
status = b'200 OK' # HTTP Status
A C implementation of this API is available as :mod:`xml.etree.cElementTree`.
See http://effbot.org/zone/element-index.htm for tutorials and links to other
-docs. Fredrik Lundh's page is also the location of the development version of the
+docs. Fredrik Lundh's page is also the location of the development version of the
xml.etree.ElementTree.
.. _elementtree-functions:
<title>Example page</title>
</head>
<body>
- <p>Moved to <a href="http://example.org/">example.org</a>
+ <p>Moved to <a href="http://example.org/">example.org</a>
or <a href="http://example.com/">example.com</a>.</p>
</body>
</html>
:meth:`XMLTreeBuilder.feed` calls *target*\'s :meth:`start` method
for each opening tag, its :meth:`end` method for each closing tag,
-and data is processed by method :meth:`data`. :meth:`XMLTreeBuilder.close`
-calls *target*\'s method :meth:`close`.
-:class:`XMLTreeBuilder` can be used not only for building a tree structure.
+and data is processed by method :meth:`data`. :meth:`XMLTreeBuilder.close`
+calls *target*\'s method :meth:`close`.
+:class:`XMLTreeBuilder` can be used not only for building a tree structure.
This is an example of counting the maximum depth of an XML file::
>>> from xml.etree.ElementTree import XMLTreeBuilder
... maxDepth = 0
... depth = 0
... def start(self, tag, attrib): # Called for each opening tag.
- ... self.depth += 1
+ ... self.depth += 1
... if self.depth > self.maxDepth:
... self.maxDepth = self.depth
... def end(self, tag): # Called for each closing tag.
... self.depth -= 1
- ... def data(self, data):
+ ... def data(self, data):
... pass # We do not need to do anything with data.
... def close(self): # Called when all data has been parsed.
... return self.maxDepth
- ...
+ ...
>>> target = MaxDepth()
>>> parser = XMLTreeBuilder(target=target)
>>> exampleXml = """
requestHandler=RequestHandler)
server.register_introspection_functions()
- # Register pow() function; this will use the value of
+ # Register pow() function; this will use the value of
# pow.__name__ as the name, which is just 'pow'.
server.register_function(pow)
return x + y
server.register_function(adder_function, 'add')
- # Register an instance; all the methods of the instance are
+ # Register an instance; all the methods of the instance are
# published as XML-RPC methods (in this case, just 'div').
class MyFuncs:
- def div(self, x, y):
+ def div(self, x, y):
return x // y
server.register_instance(MyFuncs())
.. method:: ZipFile.extractall([path[, members[, pwd]]])
- Extract all members from the archive to the current working directory. *path*
+ Extract all members from the archive to the current working directory. *path*
specifies a different directory to extract to. *members* is optional and must
be a subset of the list returned by :meth:`namelist`. *pwd* is the password
used for encrypted files.
.. note::
- When passing a :class:`ZipInfo` instance as the *zinfo_or_acrname* parameter,
- the compression method used will be that specified in the *compress_type*
- member of the given :class:`ZipInfo` instance. By default, the
+ When passing a :class:`ZipInfo` instance as the *zinfo_or_acrname* parameter,
+ the compression method used will be that specified in the *compress_type*
+ member of the given :class:`ZipInfo` instance. By default, the
:class:`ZipInfo` constructor sets this member to :const:`ZIP_STORED`.
The following data attributes are also available:
.. attribute:: ZipFile.comment
- The comment text associated with the ZIP file. If assigning a comment to a
- :class:`ZipFile` instance created with mode 'a' or 'w', this should be a
- string no longer than 65535 bytes. Comments longer than this will be
+ The comment text associated with the ZIP file. If assigning a comment to a
+ :class:`ZipFile` instance created with mode 'a' or 'w', this should be a
+ string no longer than 65535 bytes. Comments longer than this will be
truncated in the written archive when :meth:`ZipFile.close` is called.
.. _pyzipfile-objects:
internal use only. The :meth:`writepy` method makes archives with file names
like this::
- string.pyc # Top level name
- test/__init__.pyc # Package directory
+ string.pyc # Top level name
+ test/__init__.pyc # Package directory
test/testall.pyc # Module test.testall
- test/bogus/__init__.pyc # Subpackage directory
+ test/bogus/__init__.pyc # Subpackage directory
test/bogus/myfile.pyc # Submodule test.bogus.myfile
-------- -------
8467 1 file
$ ./python
- Python 2.3 (#1, Aug 1 2003, 19:54:32)
+ Python 2.3 (#1, Aug 1 2003, 19:54:32)
>>> import sys
>>> sys.path.insert(0, '/tmp/example.zip') # Add .zip file to front of path
>>> import jwzthreading
The source for the :mod:`fpectl` module includes the following notice::
- ---------------------------------------------------------------------
- / Copyright (c) 1996. \
+ ---------------------------------------------------------------------
+ / Copyright (c) 1996. \
| The Regents of the University of California. |
| All rights reserved. |
| |
| opinions of authors expressed herein do not necessarily state or |
| reflect those of the United States Government or the University |
| of California, and shall not be used for advertising or product |
- \ endorsement purposes. /
+ \ endorsement purposes. /
---------------------------------------------------------------------
implementing :meth:`__format__`, however most classes will either
delegate formatting to one of the built-in types, or use a similar
formatting option syntax.
-
+
See :ref:`formatspec` for a description of the standard formatting syntax.
The return value must be a string object.
:keyword:`del` statements. The syntax for a slicing:
.. productionlist::
- slicing: `primary` "[" `slice_list` "]"
+ slicing: `primary` "[" `slice_list` "]"
slice_list: `slice_item` ("," `slice_item`)* [","]
slice_item: `expression` | `proper_slice`
proper_slice: [`lower_bound`] ":" [`upper_bound`] [ ":" [`stride`] ]
the call.
.. note::
-
+
An implementation may provide builtin functions whose positional parameters do
not have names, even if they are 'named' for the purpose of documentation, and
which therefore cannot be supplied by keyword. In CPython, this is the case for
Comparison of objects of the differing types depends on whether either
of the types provide explicit support for the comparison. Most numeric types
can be compared with one another, but comparisons of :class:`float` and
-:class:`Decimal` are not supported to avoid the inevitable confusion arising
+:class:`Decimal` are not supported to avoid the inevitable confusion arising
from representation issues such as ``float('1.1')`` being inexactly represented
and therefore not exactly equal to ``Decimal('1.1')`` which is. When
cross-type comparison is not supported, the comparison method returns
identity only, but this caused surprises because people expected to be able
to test a dictionary for emptiness by comparing it to ``{}``.
-.. [#] Due to automatic garbage-collection, free lists, and the dynamic nature of
+.. [#] Due to automatic garbage-collection, free lists, and the dynamic nature of
descriptors, you may notice seemingly unusual behaviour in certain uses of
the :keyword:`is` operator, like those involving comparisons between instance
methods, or constants. Check their documentation for more info.
7 2147483647 0o177 0b100110111
3 79228162514264337593543950336 0o377 0x100000000
- 79228162514264337593543950336 0xdeadbeef
+ 79228162514264337593543950336 0xdeadbeef
.. _floating:
part, add a floating point number to it, e.g., ``(3+4j)``. Some examples of
imaginary literals::
- 3.14j 10.j 10j .001j 1e100j 3.14e-10j
+ 3.14j 10.j 10j .001j 1e100j 3.14e-10j
.. _operators:
.. index:: pair: exception; chaining
__cause__ (exception attribute)
__context__ (exception attribute)
-
+
The ``from`` clause is used for exception chaining: if given, the second
*expression* must be another exception class or instance, which will then be
attached to the raised exception as the :attr:`__cause__` attribute (which is
searched inside the package. A package is generally a subdirectory of a
directory on ``sys.path`` that has a file :file:`__init__.py`.
-..
+..
[XXX Can't be
bothered to spell this out right now; see the URL
http://www.python.org/doc/essays/packages.html for more details, also about how
: ["=" (`target_list` "=")+ `expression_list`]
: | "nonlocal" `identifier` `augop` `expression_list`
-The :keyword:`nonlocal` statement causes the listed identifiers to refer to
-previously bound variables in the nearest enclosing scope. This is important
-because the default behavior for binding is to search the local namespace
+The :keyword:`nonlocal` statement causes the listed identifiers to refer to
+previously bound variables in the nearest enclosing scope. This is important
+because the default behavior for binding is to search the local namespace
first. The statement allows encapsulated code to rebind variables outside of
the local scope besides the global (module) scope.
enclosing scope (the scope in which a new binding should be created cannot
be determined unambiguously).
-Names listed in a :keyword:`nonlocal` statement must not collide with
+Names listed in a :keyword:`nonlocal` statement must not collide with
pre-existing bindings in the local scope.
.. seealso::
class or classes, and a method can call the method of a base class with the same
name. Objects can contain an arbitrary amount of private data.
-In C++ terminology, normally class members (including the data members) are
+In C++ terminology, normally class members (including the data members) are
*public* (except see below :ref:`tut-private`),
and all member functions are *virtual*. There are no special constructors or
destructors. As in Modula-3, there are no shorthands for referencing the
def do_global():
global spam
spam = "global spam"
-
+
spam = "test spam"
do_local()
print("After local assignment:", spam)
... def __init__(self, realpart, imagpart):
... self.r = realpart
... self.i = imagpart
- ...
+ ...
>>> x = Complex(3.0, -4.5)
>>> x.r, x.i
(3.0, -4.5)
is ``True`` since :class:`bool` is a subclass of :class:`int`. However,
``issubclass(float, int)`` is ``False`` since :class:`float` is not a
subclass of :class:`int`.
-
+
.. _tut-multiple:
... a = ['cat', 'window', 'defenestrate']
>>> for x in a:
... print(x, len(x))
- ...
+ ...
cat 3
window 6
defenestrate 12
>>> for x in a[:]: # make a slice copy of the entire list
... if len(x) > 6: a.insert(0, x)
- ...
+ ...
>>> a
['defenestrate', 'cat', 'window', 'defenestrate']
2
3
4
-
+
The given end point is never part of the generated list; ``range(10)`` generates
is possible to let the range start at another number, or to specify a different
increment (even negative; sometimes this is called the 'step')::
- range(5, 10)
+ range(5, 10)
5 through 9
- range(0, 10, 3)
+ range(0, 10, 3)
0, 3, 6, 9
- range(-10, -100, -30)
+ range(-10, -100, -30)
-10, -40, -70
To iterate over the indices of a sequence, you can combine :func:`range` and
>>> a = ['Mary', 'had', 'a', 'little', 'lamb']
>>> for i in range(len(a)):
... print(i, a[i])
- ...
+ ...
0 Mary
1 had
2 a
range(0, 10)
In many ways the object returned by :func:`range` behaves as if it is a list,
-but in fact it isn't. It is an object which returns the successive items of
-the desired sequence when you iterate over it, but it doesn't really make
-the list, thus saving space.
+but in fact it isn't. It is an object which returns the successive items of
+the desired sequence when you iterate over it, but it doesn't really make
+the list, thus saving space.
-We say such an object is *iterable*, that is, suitable as a target for
-functions and constructs that expect something from which they can
+We say such an object is *iterable*, that is, suitable as a target for
+functions and constructs that expect something from which they can
obtain successive items until the supply is exhausted. We have seen that
the :keyword:`for` statement is such an *iterator*. The function :func:`list`
is another; it creates lists from iterables::
... else:
... # loop fell through without finding a factor
... print(n, 'is a prime number')
- ...
+ ...
2 is a prime number
3 is a prime number
4 equals 2 * 2
>>> while True:
... pass # Busy-wait for keyboard interrupt (Ctrl+C)
- ...
+ ...
This is commonly used for creating minimal classes::
>>> def initlog(*args):
... pass # Remember to implement this!
- ...
+ ...
.. _tut-functions:
... print(b, end=' ')
... a, b = b, a+b
... print()
- ...
+ ...
>>> # Now call the function we just defined:
... fib(2000)
1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597
... result.append(b) # see below
... a, b = b, a+b
... return result
- ...
+ ...
>>> f100 = fib2(100) # call it
>>> f100 # write the result
[1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89]
>>> def function(a):
... pass
- ...
+ ...
>>> function(0, a=0)
Traceback (most recent call last):
File "<stdin>", line 1, in ?
------------------------
.. index::
- statement: *
+ statement: *
Finally, the least frequently used option is to specify that a function can be
called with an arbitrary number of arguments. These arguments will be wrapped
def write_multiple_items(file, separator, *args):
file.write(separator.join(args))
-
+
Normally, these ``variadic`` arguments will be last in the list of formal
-parameters, because they scoop up all remaining input arguments that are
+parameters, because they scoop up all remaining input arguments that are
passed to the function. Any formal parameters which occur after the ``*args``
-parameter are 'keyword-only' arguments, meaning that they can only be used as
+parameter are 'keyword-only' arguments, meaning that they can only be used as
keywords rather than positional arguments. ::
-
+
>>> def concat(*args, sep="/"):
... return sep.join(args)
...
single: strings, documentation
Here are some conventions about the content and formatting of documentation
-strings.
+strings.
The first line should always be a short, concise summary of the object's
purpose. For brevity, it should not explicitly state the object's name or type,
>>> def my_function():
... """Do nothing, but document it.
- ...
+ ...
... No, really, it doesn't do anything.
... """
... pass
- ...
+ ...
>>> print(my_function.__doc__)
Do nothing, but document it.
List comprehensions provide a concise way to create lists from sequences.
Common applications are to make lists where each element is the result of
-some operations applied to each member of the sequence, or to create a
+some operations applied to each member of the sequence, or to create a
subsequence of those elements that satisfy a certain condition.
clause, then zero or more :keyword:`for` or :keyword:`if` clauses. The result
will be a list resulting from evaluating the expression in the context of the
:keyword:`for` and :keyword:`if` clauses which follow it. If the expression
-would evaluate to a tuple, it must be parenthesized.
+would evaluate to a tuple, it must be parenthesized.
Here we take a list of numbers and return a list of three times each number::
powerful tool but -- like all powerful tools -- they need to be used carefully,
if at all.
-Consider the following example of a 3x3 matrix held as a list containing three
+Consider the following example of a 3x3 matrix held as a list containing three
lists, one list per row::
>>> mat = [
... [7, 8, 9],
... ]
-Now, if you wanted to swap rows and columns, you could use a list
+Now, if you wanted to swap rows and columns, you could use a list
comprehension::
>>> print([[row[i] for row in mat] for i in [0, 1, 2]])
print(row[i], end="")
print()
-In real world, you should prefer builtin functions to complex flow statements.
+In real world, you should prefer builtin functions to complex flow statements.
The :func:`zip` function would do a great job for this use case::
>>> list(zip(*mat))
... break
... except ValueError:
... print("Oops! That was no valid number. Try again...")
- ...
+ ...
The :keyword:`try` statement works as follows.
>>> def this_fails():
... x = 1/0
- ...
+ ...
>>> try:
... this_fails()
... except ZeroDivisionError as err:
... print('Handling run-time error:', err)
- ...
+ ...
Handling run-time error: int division or modulo by zero
... self.value = value
... def __str__(self):
... return repr(self.value)
- ...
+ ...
>>> try:
... raise MyError(2*2)
... except MyError as e:
... print('My exception occurred, value:', e.value)
- ...
+ ...
My exception occurred, value: 4
>>> raise MyError('oops!')
Traceback (most recent call last):
... raise KeyboardInterrupt
... finally:
... print('Goodbye, world!')
- ...
+ ...
Goodbye, world!
Traceback (most recent call last):
File "<stdin>", line 2, in ?
print(line)
The problem with this code is that it leaves the file open for an indeterminate
-amount of time after this part of the code has finished executing.
-This is not an issue in simple scripts, but can be a problem for larger
-applications. The :keyword:`with` statement allows objects like files to be
+amount of time after this part of the code has finished executing.
+This is not an issue in simple scripts, but can be a problem for larger
+applications. The :keyword:`with` statement allows objects like files to be
used in a way that ensures they are always cleaned up promptly and correctly. ::
with open("myfile.txt") as f:
.. _tutorial-index:
######################
- The Python Tutorial
+ The Python Tutorial
######################
:Release: |version|
>>> for x in range(1, 11):
... print('{0:2d} {1:3d} {2:4d}'.format(x, x*x, x*x*x))
- ...
+ ...
1 1 1
2 4 8
3 9 27
>>> table = {'Sjoerd': 4127, 'Jack': 4098, 'Dcab': 7678}
>>> for name, phone in table.items():
... print('{0:10} ==> {1:10d}'.format(name, phone))
- ...
+ ...
Jack ==> 4098
Dcab ==> 7678
Sjoerd ==> 4127
16
>>> f.seek(5) # Go to the 6th byte in the file
5
- >>> f.read(1)
+ >>> f.read(1)
b'5'
>>> f.seek(-3, 2) # Go to the 3rd byte before the end
13
In text files (those opened without a ``b`` in the mode string), only seeks
relative to the beginning of the file are allowed (the exception being seeking
to the very file end with ``seek(0, 2)``).
-
+
When you're done with a file, call ``f.close()`` to close it and free up any
system resources taken up by the open file. After calling ``f.close()``,
attempts to use the file object will automatically fail. ::
>>> the_world_is_flat = 1
>>> if the_world_is_flat:
... print("Be careful not to fall off!")
- ...
+ ...
Be careful not to fall off!
to do this, put one more special comment line right after the ``#!`` line to
define the source file encoding::
- # -*- coding: encoding -*-
+ # -*- coding: encoding -*-
With that declaration, everything in the source file will be treated as having
the encoding *encoding* instead of UTF-8. The list of possible encodings can be
>>> 8/5 # Fractions aren't lost when dividing integers
1.6000000000000001
-Note: You might not see exactly the same result; floating point results can
+Note: You might not see exactly the same result; floating point results can
differ from one machine to another. We will say more later about controlling
the appearance of floating point output; what we see here is the most
informative display but not as easy to read as we would get with::
why these two ways of displaying floating point data come to be different.
See :ref:`tut-fp-issues` for a full discussion.
-To do integer division and get an integer result,
+To do integer division and get an integer result,
discarding any fractional result, there is another operator, ``//``::
-
+
>>> # Integer division returns the floor:
... 7//3
2
>>> # try to access an undefined variable
... n
- Traceback (most recent call last):
+ Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'n' is not defined
they will be included in the string. ::
print("""
- Usage: thingy [OPTIONS]
+ Usage: thingy [OPTIONS]
-h Display this usage message
-H hostname Hostname to connect to
""")
produces the following output::
- Usage: thingy [OPTIONS]
+ Usage: thingy [OPTIONS]
-h Display this usage message
-H hostname Hostname to connect to
Then the right edge of the last character of a string of *n* characters has
index *n*, for example::
- +---+---+---+---+---+
+ +---+---+---+---+---+
| H | e | l | p | A |
- +---+---+---+---+---+
- 0 1 2 3 4 5
+ +---+---+---+---+---+
+ 0 1 2 3 4 5
-5 -4 -3 -2 -1
The first row of numbers gives the position of the indices 0...5 in the string;
.. seealso::
:ref:`typesseq`
- Strings are examples of *sequence types*, and support the common
+ Strings are examples of *sequence types*, and support the common
operations supported by such types.
:ref:`string-methods`
>>> while b < 10:
... print(b)
... a, b = b, a+b
- ...
+ ...
1
1
2
* The :func:`print` function writes the value of the expression(s) it is
given. It differs from just writing the expression you want to write (as we did
- earlier in the calculator examples) in the way it handles multiple
- expressions, floating point quantities,
+ earlier in the calculator examples) in the way it handles multiple
+ expressions, floating point quantities,
and strings. Strings are printed without quotes, and a space is inserted
between items, so you can format things nicely, like this::
>>> while b < 1000:
... print(b, end=' ')
... a, b = b, a+b
- ...
+ ...
1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987
1 1 2 3 5 8 13 21 34 55 89 144 233 377
This imports all names except those beginning with an underscore (``_``).
-In most cases Python programmers do not use this facility since it introduces
-an unknown set of names into the interpreter, possibly hiding some things
+In most cases Python programmers do not use this facility since it introduces
+an unknown set of names into the interpreter, possibly hiding some things
you have already defined.
.. note::
['__name__', 'fib', 'fib2']
>>> dir(sys)
['__displayhook__', '__doc__', '__excepthook__', '__name__', '__stderr__',
- '__stdin__', '__stdout__', '_getframe', 'api_version', 'argv',
+ '__stdin__', '__stdout__', '_getframe', 'api_version', 'argv',
'builtin_module_names', 'byteorder', 'callstats', 'copyright',
'displayhook', 'exc_info', 'excepthook',
'exec_prefix', 'executable', 'exit', 'getdefaultencoding', 'getdlopenflags',
>>> dir(builtins)
['ArithmeticError', 'AssertionError', 'AttributeError', 'BaseException', 'Buffer
- Error', 'DeprecationWarning', 'EOFError', 'Ellipsis', 'EnvironmentError', 'Excep
- tion', 'False', 'FloatingPointError', 'FutureWarning', 'GeneratorExit', 'IOError
- ', 'ImportError', 'ImportWarning', 'IndentationError', 'IndexError', 'KeyError',
- 'KeyboardInterrupt', 'LookupError', 'MemoryError', 'NameError', 'None', 'NotImp
- lemented', 'NotImplementedError', 'OSError', 'OverflowError', 'PendingDeprecatio
- nWarning', 'ReferenceError', 'RuntimeError', 'RuntimeWarning', 'StopIteration',
- 'SyntaxError', 'SyntaxWarning', 'SystemError', 'SystemExit', 'TabError', 'True',
- 'TypeError', 'UnboundLocalError', 'UnicodeDecodeError', 'UnicodeEncodeError', '
- UnicodeError', 'UnicodeTranslateError', 'UnicodeWarning', 'UserWarning', 'ValueE
- rror', 'Warning', 'ZeroDivisionError', '__build_class__', '__debug__', '__doc__'
- , '__import__', '__name__', 'abs', 'all', 'any', 'basestring', 'bin', 'bool', 'b
- uffer', 'bytes', 'chr', 'chr8', 'classmethod', 'cmp', 'compile', 'complex', 'cop
- yright', 'credits', 'delattr', 'dict', 'dir', 'divmod', 'enumerate', 'eval', 'ex
- ec', 'exit', 'filter', 'float', 'frozenset', 'getattr', 'globals', 'hasattr', 'h
- ash', 'help', 'hex', 'id', 'input', 'int', 'isinstance', 'issubclass', 'iter', '
- len', 'license', 'list', 'locals', 'map', 'max', 'memoryview', 'min', 'next', 'o
- bject', 'oct', 'open', 'ord', 'pow', 'print', 'property', 'quit', 'range', 'repr
- ', 'reversed', 'round', 'set', 'setattr', 'slice', 'sorted', 'staticmethod', 'st
- r', 'str8', 'sum', 'super', 'trunc', 'tuple', 'type', 'vars', 'zip']
+ Error', 'DeprecationWarning', 'EOFError', 'Ellipsis', 'EnvironmentError', 'Excep
+ tion', 'False', 'FloatingPointError', 'FutureWarning', 'GeneratorExit', 'IOError
+ ', 'ImportError', 'ImportWarning', 'IndentationError', 'IndexError', 'KeyError',
+ 'KeyboardInterrupt', 'LookupError', 'MemoryError', 'NameError', 'None', 'NotImp
+ lemented', 'NotImplementedError', 'OSError', 'OverflowError', 'PendingDeprecatio
+ nWarning', 'ReferenceError', 'RuntimeError', 'RuntimeWarning', 'StopIteration',
+ 'SyntaxError', 'SyntaxWarning', 'SystemError', 'SystemExit', 'TabError', 'True',
+ 'TypeError', 'UnboundLocalError', 'UnicodeDecodeError', 'UnicodeEncodeError', '
+ UnicodeError', 'UnicodeTranslateError', 'UnicodeWarning', 'UserWarning', 'ValueE
+ rror', 'Warning', 'ZeroDivisionError', '__build_class__', '__debug__', '__doc__'
+ , '__import__', '__name__', 'abs', 'all', 'any', 'basestring', 'bin', 'bool', 'b
+ uffer', 'bytes', 'chr', 'chr8', 'classmethod', 'cmp', 'compile', 'complex', 'cop
+ yright', 'credits', 'delattr', 'dict', 'dir', 'divmod', 'enumerate', 'eval', 'ex
+ ec', 'exit', 'filter', 'float', 'frozenset', 'getattr', 'globals', 'hasattr', 'h
+ ash', 'help', 'hex', 'id', 'input', 'int', 'isinstance', 'issubclass', 'iter', '
+ len', 'license', 'list', 'locals', 'map', 'max', 'memoryview', 'min', 'next', 'o
+ bject', 'oct', 'open', 'ord', 'pow', 'print', 'property', 'quit', 'range', 'repr
+ ', 'reversed', 'round', 'set', 'setattr', 'slice', 'sorted', 'staticmethod', 'st
+ r', 'str8', 'sum', 'super', 'trunc', 'tuple', 'type', 'vars', 'zip']
.. _tut-packages:
>>> random.random() # random float
0.17970987693706186
>>> random.randrange(6) # random integer chosen from range(6)
- 4
+ 4
The SciPy project <http://scipy.org> has many other modules for numerical
computations.
class AsyncZip(threading.Thread):
def __init__(self, infile, outfile):
- threading.Thread.__init__(self)
+ threading.Thread.__init__(self)
self.infile = infile
self.outfile = outfile
def run(self):
results in decimal floating point and binary floating point. The difference
becomes significant if the results are rounded to the nearest cent::
- >>> from decimal import *
+ >>> from decimal import *
>>> Decimal('0.70') * Decimal('1.05')
Decimal("0.7350")
>>> .70 * 1.05
- 0.73499999999999999
+ 0.73499999999999999
The :class:`Decimal` result keeps a trailing zero, automatically inferring four
place significance from multiplicands with two place significance. Decimal
>>> sum([Decimal('0.1')]*10) == Decimal('1.0')
True
>>> sum([0.1]*10) == 1.0
- False
+ False
The :mod:`decimal` module provides arithmetic with as much precision as needed::
Cookbook (O'Reilly & Associates, ISBN 0-596-00797-3.)
* http://scipy.org: The Scientific Python project includes modules for fast
- array computations and manipulations plus a host of packages for such
- things as linear algebra, Fourier transforms, non-linear solvers,
+ array computations and manipulations plus a host of packages for such
+ things as linear algebra, Fourier transforms, non-linear solvers,
random number distributions, statistical analysis and the like.
For Python-related questions and problem reports, you can post to the newsgroup
.. Postings figure based on average of last six months activity as
reported by www.egroups.com; Jan. 2000 - June 2000: 21272 msgs / 182
- days = 116.9 msgs / day and steadily increasing. (XXX up to date figures?)
+ days = 116.9 msgs / day and steadily increasing. (XXX up to date figures?)
The CPython interpreter scans the command line and the environment for various
settings.
-.. note::
-
+.. note::
+
Other implementations' command line schemes may differ. See
:ref:`implementations` for further resources.
Execute the Python code in *command*. *command* can be one ore more
statements separated by newlines, with significant leading whitespace as in
normal module code.
-
+
If this option is given, the first element of :data:`sys.argv` will be
``"-c"`` and the current directory will be added to the start of
:data:`sys.path` (allowing modules in that directory to be imported as top
Search :data:`sys.path` for the named module and execute its contents as
the :mod:`__main__` module.
-
+
Since the argument is a *module* name, you must not give a file extension
(``.py``). The ``module-name`` should be a valid Python module name, but
the implementation may not always enforce this (e.g. it may allow you to
written in C, since they do not have Python module files. However, it
can still be used for precompiled modules, even if the original source
file is not available.
-
+
If this option is given, the first element of :data:`sys.argv` will be the
full path to the module file. As with the :option:`-c` option, the current
directory will be added to the start of :data:`sys.path`.
-
+
Many standard library modules contain code that is invoked on their execution
as a script. An example is the :mod:`timeit` module::
python -mtimeit -s 'setup here' 'benchmarked code here'
python -mtimeit -h # for details
- .. seealso::
+ .. seealso::
:func:`runpy.run_module`
The actual implementation of this feature.
--version
Print the Python version number and exit. Example output could be::
-
+
Python 3.0
enter interactive mode after executing the script or the command, even when
:data:`sys.stdin` does not appear to be a terminal. The
:envvar:`PYTHONSTARTUP` file is not read.
-
+
This can be useful to inspect global variables or a stack trace when a script
raises an exception. See also :envvar:`PYTHONINSPECT`.
.. cmdoption:: -u
-
+
Force stdin, stdout and stderr to be totally unbuffered. On systems where it
matters, also put stdin, stdout and stderr in binary mode.
-
+
Note that there is internal buffering in :meth:`file.readlines` and
:ref:`bltin-file-objects` (``for line in sys.stdin``) which is not influenced
by this option. To work around this, you will want to use
.. XXX should the -U option be documented?
.. cmdoption:: -v
-
+
Print a message each time a module is initialized, showing the place
(filename or built-in module) from which it is loaded. When given twice
(:option:`-vv`), print a message for each file that is checked for when
.. cmdoption:: -W arg
-
+
Warning control. Python's warning machinery by default prints warning
messages to :data:`sys.stderr`. A typical warning message has the following
form::
file:line: category: message
-
+
By default, each warning is printed once for each source line where it
occurs. This option controls how often warnings are printed.
one option, the action for the last matching option is performed. Invalid
:option:`-W` options are ignored (though, a warning message is printed about
invalid options when the first warning is issued).
-
+
Warnings can also be controlled from within a Python program using the
:mod:`warnings` module.
The simplest form of argument is one of the following action strings (or a
unique abbreviation):
-
+
``ignore``
Ignore all warnings.
``default``
Print each warning only the first time it occurs in the program.
``error``
Raise an exception instead of printing a warning message.
-
- The full form of argument is::
-
+
+ The full form of argument is::
+
action:message:category:module:line
Here, *action* is as explained above but only applies to messages that match
.. cmdoption:: -x
-
+
Skip the first line of the source, allowing use of non-Unix forms of
``#!cmd``. This is intended for a DOS specific hack only.
-
+
.. warning:: The line numbers in error messages will be off by one!
.. _using-on-envvars:
These environment variables influence Python's behavior.
.. envvar:: PYTHONHOME
-
+
Change the location of the standard Python libraries. By default, the
libraries are searched in :file:`{prefix}/lib/python{version}` and
:file:`{exec_prefix}/lib/python{version}`, where :file:`{prefix}` and
:file:`{exec_prefix}` are installation-dependent directories, both defaulting
to :file:`/usr/local`.
-
+
When :envvar:`PYTHONHOME` is set to a single directory, its value replaces
both :file:`{prefix}` and :file:`{exec_prefix}`. To specify different values
for these, set :envvar:`PYTHONHOME` to :file:`{prefix}:{exec_prefix}`.
In addition to normal directories, individual :envvar:`PYTHONPATH` entries
may refer to zipfiles containing pure Python modules (in either source or
compiled form). Extension modules cannot be imported from zipfiles.
-
+
The default search path is installation dependent, but generally begins with
:file:`{prefix}/lib/python{version}`` (see :envvar:`PYTHONHOME` above). It
is *always* appended to :envvar:`PYTHONPATH`.
-
+
An additional directory will be inserted in the search path in front of
:envvar:`PYTHONPATH` as described above under
:ref:`using-on-interface-options`. The search path can be manipulated from
.. envvar:: PYTHONSTARTUP
-
+
If this is the name of a readable file, the Python commands in that file are
executed before the first prompt is displayed in interactive mode. The file
is executed in the same namespace where interactive commands are executed so
.. envvar:: PYTHONY2K
-
+
Set this to a non-empty string to cause the :mod:`time` module to require
dates specified as strings to include 4-digit years, otherwise 2-digit years
are converted based on rules described in the :mod:`time` module
.. envvar:: PYTHONOPTIMIZE
-
+
If this is set to a non-empty string it is equivalent to specifying the
:option:`-O` option. If set to an integer, it is equivalent to specifying
:option:`-O` multiple times.
.. envvar:: PYTHONDEBUG
-
+
If this is set to a non-empty string it is equivalent to specifying the
:option:`-d` option. If set to an integer, it is equivalent to specifying
:option:`-d` multiple times.
.. envvar:: PYTHONINSPECT
-
+
If this is set to a non-empty string it is equivalent to specifying the
:option:`-i` option.
.. envvar:: PYTHONUNBUFFERED
-
+
If this is set to a non-empty string it is equivalent to specifying the
:option:`-u` option.
.. envvar:: PYTHONVERBOSE
-
+
If this is set to a non-empty string it is equivalent to specifying the
:option:`-v` option. If set to an integer, it is equivalent to specifying
:option:`-v` multiple times.
.. envvar:: PYTHONCASEOK
-
+
If this is set, Python ignores case in :keyword:`import` statements. This
only works on Windows.
* OpenBSD users use::
- pkg_add ftp://ftp.openbsd.org/pub/OpenBSD/4.2/packages/<insert your architecture here>/python-<version>.tgz
+ pkg_add ftp://ftp.openbsd.org/pub/OpenBSD/4.2/packages/<insert your architecture here>/python-<version>.tgz
For example i386 users get the 2.5.1 version of Python using::
Python-related paths and files
==============================
-
+
These are subject to difference depending on local installation conventions;
:envvar:`prefix` (``${prefix}``) and :envvar:`exec_prefix` (``${exec_prefix}``)
are installation-dependent and should be interpreted as for GNU software; they
| | by the user module; not used by default |
| | or by most applications. |
+-----------------------------------------------+------------------------------------------+
-
+
Miscellaneous
=============
---------------------------------------
Windows has a built-in dialog for changing environment variables (following
-guide applies to XP classical view): Right-click the icon for your machine
-(usually located on your Desktop and called "My Computer") and choose
-:menuselection:`Properties` there. Then, open the :guilabel:`Advanced` tab
+guide applies to XP classical view): Right-click the icon for your machine
+(usually located on your Desktop and called "My Computer") and choose
+:menuselection:`Properties` there. Then, open the :guilabel:`Advanced` tab
and click the :guilabel:`Environment Variables` button.
In short, your path is:
#. Launch a command prompt.
#. Associate the correct file group with ``.py`` scripts::
-
+
assoc .py=Python.File
#. Redirect all Python files to the new executable::
-
+
ftype Python.File=C:\Path\to\pythonw.exe "%1" %*
****************************
- What's New in Python 2.0
+ What's New in Python 2.0
****************************
:Author: A.M. Kuchling and Moshe Zadka
finding all the strings in the list containing a given substring. You could
write the following to do it::
- # Given the list L, make a list of all strings
+ # Given the list L, make a list of all strings
# containing the substring S.
- sublist = filter( lambda s, substring=S:
+ sublist = filter( lambda s, substring=S:
string.find(s, substring) != -1,
L)
List comprehensions have the form::
- [ expression for expr in sequence1
+ [ expression for expr in sequence1
for expr2 in sequence2 ...
for exprN in sequenceN
if condition ]
...
for exprN in sequenceN:
if (condition):
- # Append the value of
- # the expression to the
+ # Append the value of
+ # the expression to the
# resulting list.
This means that when there are multiple :keyword:`for`...\ :keyword:`in`
def f():
print "i=",i
- i = i + 1
+ i = i + 1
f()
Two new exceptions, :exc:`TabError` and :exc:`IndentationError`, have been
the following lines of code::
if dict.has_key( key ): return dict[key]
- else:
+ else:
dict[key] = []
return dict[key]
:file:`setup.py` can be just a few lines long::
from distutils.core import setup
- setup (name = "foo", version = "1.0",
+ setup (name = "foo", version = "1.0",
py_modules = ["module1", "module2"])
The :file:`setup.py` file isn't much more complicated if the software consists
of a few packages::
from distutils.core import setup
- setup (name = "foo", version = "1.0",
+ setup (name = "foo", version = "1.0",
packages = ["package", "package.subpackage"])
A C extension can be the most complicated case; here's an example taken from
'extensions/expat/xmltok/xmlrole.c',
]
)
- setup (name = "PyXML", version = "0.5.4",
+ setup (name = "PyXML", version = "0.5.4",
ext_modules =[ expat_extension ] )
The Distutils can also take care of creating source and binary distributions.
****************************
- What's New in Python 2.1
+ What's New in Python 2.1
****************************
:Author: A.M. Kuchling
x = 1
def f():
# The next line is a syntax error
- exec 'x=2'
+ exec 'x=2'
def g():
return x
****************************
- What's New in Python 2.2
+ What's New in Python 2.2
****************************
:Author: A.M. Kuchling
Traceback (most recent call last):
File "<stdin>", line 1, in ?
StopIteration
- >>>
+ >>>
In 2.2, Python's :keyword:`for` statement no longer expects a sequence; it
expects something for which :func:`iter` will return an iterator. For backward
x = 1
def f():
# The next line is a syntax error
- exec 'x=2'
+ exec 'x=2'
def g():
return x
items = s.meerkat.getItems( {'channel': 4} )
# 'items' is another list of dictionaries, like this:
- # [{'link': 'http://freshmeat.net/releases/52719/',
- # 'description': 'A utility which converts HTML to XSL FO.',
+ # [{'link': 'http://freshmeat.net/releases/52719/',
+ # 'description': 'A utility which converts HTML to XSL FO.',
# 'title': 'html2fo 0.3 (Default)'}, ... ]
The :mod:`SimpleXMLRPCServer` module makes it easy to create straightforward
****************************
- What's New in Python 2.3
+ What's New in Python 2.3
****************************
:Author: A.M. Kuchling
-------- -------
8467 1 file
amk@nyman:~/src/python$ ./python
- Python 2.3 (#1, Aug 1 2003, 19:54:32)
+ Python 2.3 (#1, Aug 1 2003, 19:54:32)
>>> import sys
>>> sys.path.insert(0, '/tmp/example.zip') # Add .zip file to front of path
>>> import jwzthreading
# ...
}
- if (hasattr(core, 'setup_keywords') and
+ if (hasattr(core, 'setup_keywords') and
'classifiers' in core.setup_keywords):
kw['classifiers'] = \
['Topic :: Internet :: WWW/HTTP :: Dynamic Content',
creating small dictionaries::
>>> dict(red=1, blue=2, green=3, black=4)
- {'blue': 2, 'black': 4, 'green': 3, 'red': 1}
+ {'blue': 2, 'black': 4, 'green': 3, 'red': 1}
(Contributed by Just van Rossum.)
... self.valuelist.pop(i)
... def keys(self):
... return list(self.keylist)
- ...
+ ...
>>> s = SeqDict()
>>> dir(s) # See that other dictionary methods are implemented
['__cmp__', '__contains__', '__delitem__', '__doc__', '__getitem__',
set input filename
-lLENGTH, --length=LENGTH
set maximum length of output
- $
+ $
See the module's documentation for more details.
****************************
- What's New in Python 2.4
+ What's New in Python 2.4
****************************
:Author: A.M. Kuchling
>>> a.add('z') # add a new element
>>> a.update('wxy') # add multiple new elements
>>> a
- set(['a', 'c', 'b', 'd', 'r', 'w', 'y', 'x', 'z'])
+ set(['a', 'c', 'b', 'd', 'r', 'w', 'y', 'x', 'z'])
>>> a.remove('x') # take one element out
>>> a
- set(['a', 'c', 'b', 'd', 'r', 'w', 'y', 'z'])
+ set(['a', 'c', 'b', 'd', 'r', 'w', 'y', 'z'])
The :func:`frozenset` type is an immutable version of :func:`set`. Since it is
immutable and hashable, it may be used as a dictionary key or as a member of
>>> for i in reversed(xrange(1,4)):
... print i
- ...
+ ...
3
2
1
>>> input = open('/etc/passwd', 'r')
>>> for line in reversed(list(input)):
... print line
- ...
+ ...
root:*:0:0:System Administrator:/var/root:/bin/tcsh
...
28
>>> decimal.Decimal(1) / decimal.Decimal(7)
Decimal("0.1428571428571428571428571429")
- >>> decimal.getcontext().prec = 9
+ >>> decimal.getcontext().prec = 9
>>> decimal.Decimal(1) / decimal.Decimal(7)
Decimal("0.142857143")
>>> decimal.getcontext().traps[decimal.DivisionByZero] = False
>>> decimal.Decimal(1) / decimal.Decimal(0)
Decimal("Infinity")
- >>>
+ >>>
The :class:`Context` instance also has various methods for formatting numbers
such as :meth:`to_eng_string` and :meth:`to_sci_string`.
>>> 'www.python.org'.split('.', 1)
['www', 'python.org']
'www.python.org'.rsplit('.', 1)
- ['www.python', 'org']
+ ['www.python', 'org']
* Three keyword parameters, *cmp*, *key*, and *reverse*, were added to the
:meth:`sort` method of lists. These parameters make some common usages of
>>> list(d) # list the contents of the deque
['g', 'h', 'i']
>>> 'h' in d # search the deque
- True
+ True
Several modules, such as the :mod:`Queue` and :mod:`threading` modules, now take
advantage of :class:`collections.deque` for improved performance. (Contributed
>>> L = [2, 4, 6, 7, 8, 9, 11, 12, 14]
>>> for key_val, it in itertools.groupby(L, lambda x: x % 2):
... print key_val, list(it)
- ...
+ ...
0 [2, 4, 6]
1 [7]
0 [8]
1 [9, 11]
0 [12, 14]
- >>>
+ >>>
:func:`groupby` is typically used with sorted input. The logic for
:func:`groupby` is similar to the Unix ``uniq`` filter which makes it handy for
>>> word = 'abracadabra'
>>> letters = sorted(word) # Turn string into a sorted list of letters
- >>> letters
+ >>> letters
['a', 'a', 'a', 'a', 'a', 'b', 'b', 'c', 'd', 'r', 'r']
>>> for k, g in itertools.groupby(letters):
... print k, list(g)
- ...
+ ...
a ['a', 'a', 'a', 'a', 'a']
b ['b', 'b']
c ['c']
d ['d']
r ['r', 'r']
>>> # List unique letters
- >>> [k for k, g in groupby(letters)]
+ >>> [k for k, g in groupby(letters)]
['a', 'b', 'c', 'd', 'r']
>>> # Count letter occurrences
- >>> [(k, len(list(g))) for k, g in groupby(letters)]
+ >>> [(k, len(list(g))) for k, g in groupby(letters)]
[('a', 5), ('b', 2), ('c', 1), ('d', 1), ('r', 2)]
(Contributed by Hye-Shik Chang.)
import logging
logging.basicConfig(filename='/var/log/application.log',
level=0, # Log all messages
- format='%(levelname):%(process):%(thread):%(message)')
+ format='%(levelname):%(process):%(thread):%(message)')
Other additions to the :mod:`logging` package include a :meth:`log(level, msg)`
convenience method, as well as a :class:`TimedRotatingFileHandler` class that
****************************
- What's New in Python 2.5
+ What's New in Python 2.5
****************************
:Author: A.M. Kuchling
required packages. ::
VERSION = '1.0'
- setup(name='PyPackage',
+ setup(name='PyPackage',
version=VERSION,
requires=['numarray', 'zlib (>=1.1.4)'],
obsoletes=['OldPackage']
else:
else-block
finally:
- final-block
+ final-block
The code in *block-1* is executed. If the code raises an exception, the various
:keyword:`except` blocks are tested: if the exception is of class
...
except (KeyboardInterrupt, SystemExit):
raise
- except:
- # Log error...
+ except:
+ # Log error...
# Continue running program...
In Python 2.5, you can now write ``except Exception`` to achieve the same
class C:
def __index__ (self):
- return self.value
+ return self.value
The return value must be either a Python integer or long integer. The
interpreter will check that the type returned is correct, and raises a
L = ['medium', 'longest', 'short']
# Prints 'longest'
- print max(L, key=len)
+ print max(L, key=len)
# Prints 'short', because lexicographically 'short' has the largest value
- print max(L)
+ print max(L)
(Contributed by Steven Bethard and Raymond Hettinger.)
using the default ASCII encoding. The result of the comparison is false::
>>> chr(128) == unichr(128) # Can't convert chr(128) to Unicode
- __main__:1: UnicodeWarning: Unicode equal comparison failed
- to convert both arguments to Unicode - interpreting them
+ __main__:1: UnicodeWarning: Unicode equal comparison failed
+ to convert both arguments to Unicode - interpreting them
as being unequal
False
>>> chr(127) == unichr(127) # chr(127) can be converted
Printing ``index`` results in the following output::
- defaultdict(<type 'list'>, {'c': ['cammin', 'che'], 'e': ['era'],
- 'd': ['del', 'di', 'diritta'], 'm': ['mezzo', 'mi'],
- 'l': ['la'], 'o': ['oscura'], 'n': ['nel', 'nostra'],
- 'p': ['per'], 's': ['selva', 'smarrita'],
+ defaultdict(<type 'list'>, {'c': ['cammin', 'che'], 'e': ['era'],
+ 'd': ['del', 'di', 'diritta'], 'm': ['mezzo', 'mi'],
+ 'l': ['la'], 'o': ['oscura'], 'n': ['nel', 'nostra'],
+ 'p': ['per'], 's': ['selva', 'smarrita'],
'r': ['ritrovai'], 'u': ['una'], 'v': ['vita', 'via']}
(Contributed by Guido van Rossum.)
differently. ::
# Old versions
- h = md5.md5()
- h = md5.new()
+ h = md5.md5()
+ h = md5.new()
- # New version
+ # New version
h = hashlib.md5()
# Old versions
- h = sha.sha()
- h = sha.new()
+ h = sha.sha()
+ h = sha.new()
- # New version
+ # New version
h = hashlib.sha1()
# Hash that weren't previously available
case that your extensions were using it, you can replace it by something like
the following::
- range = PyObject_CallFunction((PyObject*) &PyRange_Type, "lll",
+ range = PyObject_CallFunction((PyObject*) &PyRange_Type, "lll",
start, stop, step);
.. ======================================================================
>>> import sys
>>> print 'Platform: {0.platform}\nPython version: {0.version}'.format(sys)
Platform: darwin
- Python version: 2.6a1+ (trunk:61261M, Mar 5 2008, 20:29:41)
+ Python version: 2.6a1+ (trunk:61261M, Mar 5 2008, 20:29:41)
[GCC 4.0.1 (Apple Computer, Inc. build 5367)]'
>>> import mimetypes
The primary use of :class:`bytes` in 2.6 will be to write tests of
object type such as ``isinstance(x, bytes)``. This will help the 2to3
converter, which can't tell whether 2.x code intends strings to
-contain either characters or 8-bit bytes; you can now
-use either :class:`bytes` or :class:`str` to represent your intention
+contain either characters or 8-bit bytes; you can now
+use either :class:`bytes` or :class:`str` to represent your intention
exactly, and the resulting code will also be correct in Python 3.0.
There's also a ``__future__`` import that causes all string literals
"/cgi-bin/add.py?category=1". (Contributed by Alexandre Fiori and
Nubis; :issue:`1817`.)
- The :func:`parse_qs` and :func:`parse_qsl` functions have been
+ The :func:`parse_qs` and :func:`parse_qsl` functions have been
relocated from the :mod:`cgi` module to the :mod:`urlparse` module.
- The versions still available in the :mod:`cgi` module will
+ The versions still available in the :mod:`cgi` module will
trigger :exc:`PendingDeprecationWarning` messages in 2.6
(:issue:`600362`).
* A new window method in the :mod:`curses` module,
:meth:`chgat`, changes the display attributes for a certain number of
characters on a single line. (Contributed by Fabian Kreutz.)
-
+
::
# Boldface text starting at y=0,x=21
:issue:`742598`, :issue:`1193577`.)
* The :mod:`sqlite3` module, maintained by Gerhard Haering,
- has been updated from version 2.3.2 in Python 2.5 to
+ has been updated from version 2.3.2 in Python 2.5 to
version 2.4.1.
-
+
* The :mod:`struct` module now supports the C99 :ctype:`_Bool` type,
using the format character ``'?'``.
(Contributed by David Remahl.)
``with tempfile.NamedTemporaryFile() as tmp: ...``.
(Contributed by Alexander Belopolsky; :issue:`2021`.)
-* The :mod:`test.test_support` module gained a number
- of context managers useful for writing tests.
- :func:`EnvironmentVarGuard` is a
+* The :mod:`test.test_support` module gained a number
+ of context managers useful for writing tests.
+ :func:`EnvironmentVarGuard` is a
context manager that temporarily changes environment variables and
automatically restores them to their old values.
f = urllib.urlopen('https://sf.net')
...
- Finally, :func:`check_warnings` resets the :mod:`warning` module's
+ Finally, :func:`check_warnings` resets the :mod:`warning` module's
warning filters and returns an object that will record all warning
messages triggered (:issue:`3781`)::
:meth:`activeCount` method is renamed to :meth:`active_count`. Both
the 2.6 and 3.0 versions of the module support the same properties
and renamed methods, but don't remove the old methods. No date has been set
- for the deprecation of the old APIs in Python 3.x; the old APIs won't
+ for the deprecation of the old APIs in Python 3.x; the old APIs won't
be removed in any 2.x version.
(Carried out by several people, most notably Benjamin Peterson.)
(Added by Facundo Batista.)
* The Unicode database provided by the :mod:`unicodedata` module
- has been updated to version 5.1.0. (Updated by
+ has been updated to version 5.1.0. (Updated by
Martin von Loewis; :issue:`3811`.)
* The :mod:`warnings` module's :func:`formatwarning` and :func:`showwarning`
A new function, :func:`catch_warnings`, is a context manager
intended for testing purposes that lets you temporarily modify the
warning filters and then restore their original values (:issue:`3781`).
-
+
* The XML-RPC :class:`SimpleXMLRPCServer` and :class:`DocXMLRPCServer`
classes can now be prevented from immediately opening and binding to
their socket by passing True as the ``bind_and_activate``
* :meth:`object.__init__` previously accepted arbitrary arguments and
keyword arguments, ignoring them. In Python 2.6, this is no longer
- allowed and will result in a :exc:`TypeError`. This will affect
- :meth:`__init__` methods that end up calling the corresponding
+ allowed and will result in a :exc:`TypeError`. This will affect
+ :meth:`__init__` methods that end up calling the corresponding
method on :class:`object` (perhaps through using :func:`super`).
See :issue:`1683368` for discussion.
The author would like to thank the following people for offering
suggestions, corrections and assistance with various drafts of this
-article: Georg Brandl, Steve Brown, Nick Coghlan, Ralph Corderoy,
-Jim Jewett, Kent Johnson, Chris Lambacher, Martin Michlmayr,
+article: Georg Brandl, Steve Brown, Nick Coghlan, Ralph Corderoy,
+Jim Jewett, Kent Johnson, Chris Lambacher, Martin Michlmayr,
Antoine Pitrou, Brian Warner.
****************************
- What's New In Python 3.0
+ What's New In Python 3.0
****************************
.. XXX Add trademark info for Apple, Microsoft.
.. $Id$
Rules for maintenance:
-
+
* Anyone can add text to this document. Do not spend very much time
on the wording of your changes, because your text will probably
get rewritten to some degree.
-
+
* The maintainer will go through Misc/NEWS periodically and add
changes; it's therefore more important to add your changes to
Misc/NEWS than to this file. (Note: I didn't get to this for 3.0.
GvR.)
-
+
* This is not a complete list of every single change; completeness
is the purpose of Misc/NEWS. Some changes I consider too small
or esoteric to include. If such a change is added to the text,
I'll just remove it. (This is another reason you shouldn't spend
too much time on writing your addition.)
-
+
* If you want to draw your new text to the attention of the
maintainer, add 'XXX' to the beginning of the paragraph or
section.
-
+
* It's OK to just add a fragmentary note about a change. For
example: "XXX Describe the transmogrify() function added to the
socket module." The maintainer will research the change and
write the necessary text.
-
+
* You can comment out your additions if you like, but it's not
necessary (especially when a final release is some months away).
-
+
* Credit the author of a patch or bugfix. Just the name is
sufficient; the e-mail address isn't necessary. (Due to time
constraints I haven't managed to do this for 3.0. GvR.)
-
+
* It's helpful to add the bug/patch number as a comment:
-
+
% Patch 12345
XXX Describe the transmogrify() function added to the socket
module.
(Contributed by P.Y. Developer.)
-
+
This saves the maintainer the effort of going through the SVN log
when researching a change. (Again, I didn't get to this for 3.0.
GvR.)
need it; however, 99 percent of the time an explicit :keyword:`for`
loop is more readable.
-* Removed :func:`reload`. Use :func:`imp.reload`.
+* Removed :func:`reload`. Use :func:`imp.reload`.
* Removed. :meth:`dict.has_key` -- use the :keyword:`in` operator
instead.
****************************
- What's New In Python 3.1
+ What's New In Python 3.1
****************************
.. XXX Add trademark info for Apple, Microsoft.
.. $Id$
Rules for maintenance:
-
+
* Anyone can add text to this document. Do not spend very much time
on the wording of your changes, because your text will probably
get rewritten to some degree.
-
+
* The maintainer will go through Misc/NEWS periodically and add
changes; it's therefore more important to add your changes to
Misc/NEWS than to this file. (Note: I didn't get to this for 3.0.
GvR.)
-
+
* This is not a complete list of every single change; completeness
is the purpose of Misc/NEWS. Some changes I consider too small
or esoteric to include. If such a change is added to the text,
I'll just remove it. (This is another reason you shouldn't spend
too much time on writing your addition.)
-
+
* If you want to draw your new text to the attention of the
maintainer, add 'XXX' to the beginning of the paragraph or
section.
-
+
* It's OK to just add a fragmentary note about a change. For
example: "XXX Describe the transmogrify() function added to the
socket module." The maintainer will research the change and
write the necessary text.
-
+
* You can comment out your additions if you like, but it's not
necessary (especially when a final release is some months away).
-
+
* Credit the author of a patch or bugfix. Just the name is
sufficient; the e-mail address isn't necessary. (Due to time
constraints I haven't managed to do this for 3.0. GvR.)
-
+
* It's helpful to add the bug/patch number as a comment:
-
+
% Patch 12345
XXX Describe the transmogrify() function added to the socket
module.
(Contributed by P.Y. Developer.)
-
+
This saves the maintainer the effort of going through the SVN log
when researching a change. (Again, I didn't get to this for 3.0.
GvR.)
projects / python / commitdiff