bytecode
Python source code is compiled into bytecode, the internal representation
- of a Python program in the interpreter. The bytecode is also cached in
- ``.pyc`` and ``.pyo`` files so that executing the same file is faster the
- second time (recompilation from source to bytecode can be avoided). This
- "intermediate language" is said to run on a :term:`virtual machine`
- that executes the machine code corresponding to each bytecode.
+ of a Python program in the CPython interpreter. The bytecode is also
+ cached in ``.pyc`` and ``.pyo`` files so that executing the same file is
+ faster the second time (recompilation from source to bytecode can be
+ avoided). This "intermediate language" is said to run on a
+ :term:`virtual machine` that executes the machine code corresponding to
+ each bytecode. Do note that bytecodes are not expected to work between
+ different Python virtual machines, nor to be stable between Python
+ releases.
A list of bytecode instructions can be found in the documentation for
:ref:`the dis module <bytecodes>`.
def f(...):
...
- See :ref:`the documentation for function definition <function>` for more
- about decorators.
+ The same concept exists for classes, but is less commonly used there. See
+ the documentation for :ref:`function definitions <function>` and
+ :ref:`class definitions <class>` for more about decorators.
descriptor
Any *new-style* object which defines the methods :meth:`__get__`,
well-designed code improves its flexibility by allowing polymorphic
substitution. Duck-typing avoids tests using :func:`type` or
:func:`isinstance`. (Note, however, that duck-typing can be complemented
- with :term:`abstract base class`\ es.) Instead, it typically employs
- :func:`hasattr` tests or :term:`EAFP` programming.
+ with :term:`abstract base classes <abstract base class>`.) Instead, it
+ typically employs :func:`hasattr` tests or :term:`EAFP` programming.
EAFP
Easier to ask for forgiveness than permission. This common Python coding
expression
A piece of syntax which can be evaluated to some value. In other words,
- an expression is an accumulation of expression elements like literals, names,
- attribute access, operators or function calls which all return a value.
- In contrast to many other languages, not all language constructs are expressions.
- There are also :term:`statement`\s which cannot be used as expressions,
- such as :keyword:`print` or :keyword:`if`. Assignments are also statements,
- not expressions.
+ an expression is an accumulation of expression elements like literals,
+ names, attribute access, operators or function calls which all return a
+ value. In contrast to many other languages, not all language constructs
+ are expressions. There are also :term:`statement`\s which cannot be used
+ as expressions, such as :keyword:`print` or :keyword:`if`. Assignments
+ are also statements, not expressions.
extension module
A module written in C or C++, using Python's C API to interact with the
core and with user code.
+ file object
+ An object exposing a file-oriented API (with methods such as
+ :meth:`read()` or :meth:`write()`) to an underlying resource. Depending
+ on the way it was created, a file object can mediate access to a real
+ on-disk file or to another other type of storage or communication device
+ (for example standard input/output, in-memory buffers, sockets, pipes,
+ etc.). File objects are also called :dfn:`file-like objects` or
+ :dfn:`streams`.
+
+ There are actually three categories of file objects: raw binary files,
+ buffered binary files and text files. Their interfaces are defined in the
+ :mod:`io` module. The canonical way to create a file object is by using
+ the :func:`open` function.
+
+ file-like object
+ A synonym for :term:`file object`.
+
finder
An object that tries to find the :term:`loader` for a module. It must
implement a method named :meth:`find_module`. See :pep:`302` for
slowly. See also :term:`interactive`.
iterable
- A container object capable of returning its members one at a
+ An object capable of returning its members one at a
time. Examples of iterables include all sequence types (such as
:class:`list`, :class:`str`, and :class:`tuple`) and some non-sequence
types like :class:`dict` and :class:`file` and objects of any classes you
the :term:`EAFP` approach and is characterized by the presence of many
:keyword:`if` statements.
+ In a multi-threaded environment, the LBYL approach can risk introducing a
+ race condition between "the looking" and "the leaping". For example, the
+ code, ``if key in mapping: return mapping[key]`` can fail if another
+ thread removes *key* from *mapping* after the test, but before the lookup.
+ This issue can be solved with locks or by using the EAFP approach.
+
list
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
mapping
A container object that supports arbitrary key lookups and implements the
- methods specified in the :class:`Mapping` or :class:`MutableMapping`
+ methods specified in the :class:`~collections.Mapping` or
+ :class:`~collections.MutableMapping`
:ref:`abstract base classes <collections-abstract-base-classes>`. Examples
include :class:`dict`, :class:`collections.defaultdict`,
:class:`collections.OrderedDict` and :class:`collections.Counter`.
its first :term:`argument` (which is usually called ``self``).
See :term:`function` and :term:`nested scope`.
+ method resolution order
+ Method Resolution Order is the order in which base classes are searched
+ for a member during lookup. See `The Python 2.3 Method Resolution Order
+ <http://www.python.org/download/releases/2.3/mro/>`_.
+
+ MRO
+ See :term:`method resolution order`.
+
mutable
Mutable objects can change their value but keep their :func:`id`. See
also :term:`immutable`.
nested scope
The ability to refer to a variable in an enclosing definition. For
instance, a function defined inside another function can refer to
- variables in the outer function. Note that nested scopes work only for
- 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.
+ variables in the outer function. Note that nested scopes by default work
+ only for reference and not for assignment. Local variables both read and
+ write in the innermost scope. Likewise, global variables read and write
+ to the global namespace. The :keyword:`nonlocal` allows writing to outer
+ scopes.
new-style class
Any class which inherits from :class:`object`. This includes all built-in
:term:`argument`.
Python 3000
- Nickname for the next major Python version, 3.0 (coined long ago
- when the release of version 3 was something in the distant future.) This
- is also abbreviated "Py3k".
+ Nickname for the Python 3.x release line (coined long ago when the release
+ of version 3 was something in the distant future.) This is also
+ abbreviated "Py3k".
Pythonic
An idea or piece of code which closely follows the most common idioms
object drops to zero, it is deallocated. Reference counting is
generally not visible to Python code, but it is a key element of the
:term:`CPython` implementation. The :mod:`sys` module defines a
- :func:`getrefcount` function that programmers can call to return the
+ :func:`~sys.getrefcount` function that programmers can call to return the
reference count for a particular object.
__slots__
statement
A statement is part of a suite (a "block" of code). A statement is either
an :term:`expression` or a one of several constructs with a keyword, such
- as :keyword:`if`, :keyword:`while` or :keyword:`print`.
+ as :keyword:`if`, :keyword:`while` or :keyword:`for`.
+
+ struct sequence
+ A tuple with named elements. Struct sequences expose an interface similiar
+ to :term:`named tuple` in that elements can either be accessed either by
+ index or as an attribute. However, they do not have any of the named tuple
+ methods like :meth:`~collections.somenamedtuple._make` or
+ :meth:`~collections.somenamedtuple._asdict`. Examples of struct sequences
+ include :data:`sys.float_info` and the return value of :func:`os.stat`.
triple-quoted string
A string which is bound by three instances of either a quotation mark
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