Argument Clinic (see issue for details).
support all of these scenarios. But these are advanced
topics--let's do something simpler for your first function.
+ Also, if the function has multiple calls to :c:func:`PyArg_ParseTuple`
+ or :c:func:`PyArg_ParseTupleAndKeywords` where it supports different
+ types for the same argument, or if the function uses something besides
+ PyArg_Parse functions to parse its arguments, it probably
+ isn't suitable for conversion to Argument Clinic. Argument Clinic
+ doesn't support generic functions or polymorphic parameters.
+
3. Add the following boilerplate above the function, creating our block::
/*[clinic input]
Write a pickled representation of obj to the open file.
[clinic start generated code]*/
+ The name of the class and module should be the same as the one
+ seen by Python. Check the name defined in the :c:type:`PyModuleDef`
+ or :c:type:`PyTypeObject` as appropriate.
+
+
8. Declare each of the parameters to the function. Each parameter
should get its own line. All the parameter lines should be
Advanced Topics
===============
+Now that you've had some experience working with Argument Clinic, it's time
+for some advanced topics.
+
+
+Symbolic default values
+-----------------------
+
+The default value you provide for a parameter can't be any arbitrary
+expression. Currently the following are explicitly supported:
+
+* Numeric constants (integer and float)
+* String constants
+* ``True``, ``False``, and ``None``
+* Simple symbolic constants like ``sys.maxsize``, which must
+ start with the name of the module
+
+In case you're curious, this is implemented in ``from_builtin()``
+in ``Lib/inspect.py``.
+
+(In the future, this may need to get even more elaborate,
+to allow full expressions like ``CONSTANT - 1``.)
+
Renaming the C functions generated by Argument Clinic
-----------------------------------------------------
and the impl function would now be named ``pickler_dumper_impl()``.
+The NULL default value
+----------------------
+
+For string and object parameters, you can set them to ``None`` to indicate
+that there is no default. However, that means the C variable will be
+initialized to ``Py_None``. For convenience's sakes, there's a special
+value called ``NULL`` for just this case: from Python's perspective it
+behaves like a default value of ``None``, but the C variable is initialized
+with ``NULL``.
+
+
+Converting functions using PyArg_UnpackTuple
+--------------------------------------------
+
+To convert a function parsing its arguments with :c:func:`PyArg_UnpackTuple`,
+simply write out all the arguments, specifying each as an ``object``. You
+may specify the ``type`` argument to cast the type as appropriate. All
+arguments should be marked positional-only (add a ``/`` on a line by itself
+after the last argument).
+
+Currently the generated code will use :c:func:`PyArg_ParseTuple`, but this
+will change soon.
+
Optional Groups
---------------
to achieve your first port to Argument Clinic, the walkthrough above tells
you to use "legacy converters". "Legacy converters" are a convenience,
designed explicitly to make porting existing code to Argument Clinic
-easier. And to be clear, their use is entirely acceptable when porting
-code for Python 3.4.
+easier. And to be clear, their use is acceptable when porting code for
+Python 3.4.
However, in the long term we probably want all our blocks to
use Argument Clinic's real syntax for converters. Why? A couple
restricted to what :c:func:`PyArg_ParseTuple` supports; this flexibility
won't be available to parameters using legacy converters.
-Therefore, if you don't mind a little extra effort, you should consider
-using normal converters instead of legacy converters.
+Therefore, if you don't mind a little extra effort, please use the normal
+converters instead of legacy converters.
In a nutshell, the syntax for Argument Clinic (non-legacy) converters
looks like a Python function call. However, if there are no explicit
All arguments to Argument Clinic converters are keyword-only.
All Argument Clinic converters accept the following arguments:
-``doc_default``
- If the parameter takes a default value, normally this value is also
- provided in the ``inspect.Signature`` metadata, and displayed in the
- docstring. ``doc_default`` lets you override the value used in these
- two places: pass in a string representing the Python value you wish
- to use in these two contexts.
+``py_default``
+ The default value for this parameter when defined in Python.
+ Specifically, the value that will be used in the ``inspect.Signature``
+ string.
+ If a default value is specified for the parameter, defaults to
+ ``repr(default)``, else defaults to ``None``.
+ Specified as a string.
+
+``c_default``
+ The default value for this parameter when defined in C.
+ Specifically, this will be the initializer for the variable declared
+ in the "parse function".
+ Specified as a string.
``required``
If a parameter takes a default value, Argument Clinic infers that the
Clinic that this parameter is not optional, even if it has a default
value.
+ (The need for ``required`` may be obviated by ``c_default``, which is
+ newer but arguably a better solution.)
+
``annotation``
The annotation value for this parameter. Not currently supported,
because PEP 8 mandates that the Python library may not use
``'et'`` ``str(encoding='name_of_encoding', types='bytes bytearray str')``
``'f'`` ``float``
``'h'`` ``short``
-``'H'`` ``unsigned_short``
+``'H'`` ``unsigned_short(bitwise=True)``
``'i'`` ``int``
-``'I'`` ``unsigned_int``
-``'K'`` ``unsigned_PY_LONG_LONG``
+``'I'`` ``unsigned_int(bitwise=True)``
+``'k'`` ``unsigned_long(bitwise=True)``
+``'K'`` ``unsigned_PY_LONG_LONG(bitwise=True)``
``'L'`` ``PY_LONG_LONG``
``'n'`` ``Py_ssize_t``
``'O!'`` ``object(subclass_of='&PySomething_Type')``
it accepts, along with the default value for each parameter.
Just run ``Tools/clinic/clinic.py --converters`` to see the full list.
+Py_buffer
+---------
+
+When using the ``Py_buffer`` converter
+(or the ``'s*'``, ``'w*'``, ``'*y'``, or ``'z*'`` legacy converters)
+note that the code Argument Clinic generates for you will automatically
+call :c:func:`PyBuffer_Release` on the buffer for you.
+
Advanced converters
-------------------
Currently Argument Clinic supports only a few return converters::
+ bool
int
+ unsigned int
long
+ unsigned int
+ size_t
Py_ssize_t
+ float
+ double
DecodeFSDefault
None of these take parameters. For the first three, return -1 to indicate
error. For ``DecodeFSDefault``, the return type is ``char *``; return a NULL
pointer to indicate an error.
+(There's also an experimental ``NoneType`` converter, which lets you
+return ``Py_None`` on success or ``NULL`` on failure, without having
+to increment the reference count on ``Py_None``. I'm not sure it adds
+enough clarity to be worth using.)
+
To see all the return converters Argument Clinic supports, along with
their parameters (if any),
just run ``Tools/clinic/clinic.py --converters`` for the full list.
The Python default value for this parameter, as a Python value.
Or the magic value ``unspecified`` if there is no default.
-``doc_default``
- ``default`` as it should appear in the documentation,
- as a string.
- Or ``None`` if there is no default.
- This string, when run through ``eval()``, should produce
- a Python value.
-
``py_default``
``default`` as it should appear in Python code,
as a string.
specifically the implementation of ``CReturnConverter`` and
all its subclasses.
+METH_O and METH_NOARGS
+----------------------------------------------
+
+To convert a function using ``METH_O``, make sure the function's
+single argument is using the ``object`` converter, and mark the
+arguments as positional-only::
+
+ /*[clinic input]
+ meth_o_sample
+
+ argument: object
+ /
+ [clinic start generated code]*/
+
+
+To convert a function using ``METH_NOARGS``, just don't specify
+any arguments.
+
+You can still use a self converter, a return converter, and specify
+a ``type`` argument to the object converter for ``METH_O``.
Using Argument Clinic in Python files
-------------------------------------
Tools/Demos
-----------
+- Issue #20214: Fixed a number of small issues and documentation errors in
+ Argument Clinic (see issue for details).
+
- Issue #20196: Fixed a bug where Argument Clinic did not generate correct
parsing code for functions with positional-only parameters where all arguments
are optional.
zlib_compress(PyModuleDef *module, PyObject *args)
{
PyObject *return_value = NULL;
- Py_buffer bytes = {NULL, NULL, 0, 0, 0, 0, NULL, NULL, NULL, NULL, NULL};
+ Py_buffer bytes = {NULL, NULL};
int group_right_1 = 0;
int level = 0;
return_value = zlib_compress_impl(module, &bytes, group_right_1, level);
/* Cleanup for bytes */
- if (bytes.buf)
+ if (bytes.obj)
PyBuffer_Release(&bytes);
return return_value;
static PyObject *
zlib_compress_impl(PyModuleDef *module, Py_buffer *bytes, int group_right_1, int level)
-/*[clinic end generated code: checksum=9f055a396620bc1a8a13d74c3496249528b32b0d]*/
+/*[clinic end generated code: checksum=2c59af563a4595c5ecea4011701f482ae350aa5f]*/
{
PyObject *ReturnVal = NULL;
Byte *input, *output = NULL;
zlib_Decompress_decompress(PyObject *self, PyObject *args)
{
PyObject *return_value = NULL;
- Py_buffer data = {NULL, NULL, 0, 0, 0, 0, NULL, NULL, NULL, NULL, NULL};
+ Py_buffer data = {NULL, NULL};
unsigned int max_length = 0;
if (!PyArg_ParseTuple(args,
exit:
/* Cleanup for data */
- if (data.buf)
+ if (data.obj)
PyBuffer_Release(&data);
return return_value;
static PyObject *
zlib_Decompress_decompress_impl(compobject *self, Py_buffer *data, unsigned int max_length)
-/*[clinic end generated code: checksum=5b1e4f9f1ef8eca55fff78356f9df0c81232ed3b]*/
+/*[clinic end generated code: checksum=e0058024c4a97b411d2e2197791b89fde175f76f]*/
{
int err;
unsigned int old_length, length = DEFAULTALLOC;
_empty = inspect._empty
_void = inspect._void
+NoneType = type(None)
class Unspecified:
def __repr__(self):
c.render(p, data)
positional = parameters[-1].kind == inspect.Parameter.POSITIONAL_ONLY
- if has_option_groups:
- assert positional
+ if has_option_groups and (not positional):
+ fail("You cannot use optional groups ('[' and ']')\nunless all parameters are positional-only ('/').")
# now insert our "self" (or whatever) parameters
# (we deliberately don't call render on self converters)
# Or the magic value "unspecified" if there is no default.
default = unspecified
+ # If not None, default must be isinstance() of this type.
+ # (You can also specify a tuple of types.)
+ default_type = None
+
# "default" as it should appear in the documentation, as a string.
# Or None if there is no default.
doc_default = None
self.name = name
if default is not unspecified:
+ if self.default_type and not isinstance(default, self.default_type):
+ if isinstance(self.default_type, type):
+ types_str = self.default_type.__name__
+ else:
+ types_str = ', '.join((cls.__name__ for cls in self.default_type))
+ fail("{}: default value {!r} for field {} is not of type {}".format(
+ self.__class__.__name__, default, name, types_str))
self.default = default
self.py_default = py_default if py_default is not None else py_repr(default)
self.doc_default = doc_default if doc_default is not None else self.py_default
self.c_default = c_default if c_default is not None else c_repr(default)
- elif doc_default is not None:
- fail(function.fullname + " argument " + name + " specified a 'doc_default' without having a 'default'")
+ else:
+ self.py_default = py_default
+ self.doc_default = doc_default
+ self.c_default = c_default
if annotation != unspecified:
fail("The 'annotation' parameter is not currently permitted.")
self.required = required
class bool_converter(CConverter):
type = 'int'
+ default_type = bool
format_unit = 'p'
c_ignored_default = '0'
class char_converter(CConverter):
type = 'char'
+ default_type = str
format_unit = 'c'
c_ignored_default = "'\0'"
+ def converter_init(self):
+ if len(self.default) != 1:
+ fail("char_converter: illegal default value " + repr(self.default))
+
+
@add_legacy_c_converter('B', bitwise=True)
class byte_converter(CConverter):
type = 'byte'
+ default_type = int
format_unit = 'b'
c_ignored_default = "'\0'"
class short_converter(CConverter):
type = 'short'
+ default_type = int
format_unit = 'h'
c_ignored_default = "0"
class unsigned_short_converter(CConverter):
type = 'unsigned short'
+ default_type = int
format_unit = 'H'
c_ignored_default = "0"
@add_legacy_c_converter('C', types='str')
class int_converter(CConverter):
type = 'int'
+ default_type = int
format_unit = 'i'
c_ignored_default = "0"
class unsigned_int_converter(CConverter):
type = 'unsigned int'
+ default_type = int
format_unit = 'I'
c_ignored_default = "0"
class long_converter(CConverter):
type = 'long'
+ default_type = int
format_unit = 'l'
c_ignored_default = "0"
class unsigned_long_converter(CConverter):
type = 'unsigned long'
+ default_type = int
format_unit = 'k'
c_ignored_default = "0"
class PY_LONG_LONG_converter(CConverter):
type = 'PY_LONG_LONG'
+ default_type = int
format_unit = 'L'
c_ignored_default = "0"
class unsigned_PY_LONG_LONG_converter(CConverter):
type = 'unsigned PY_LONG_LONG'
+ default_type = int
format_unit = 'K'
c_ignored_default = "0"
class Py_ssize_t_converter(CConverter):
type = 'Py_ssize_t'
+ default_type = int
format_unit = 'n'
c_ignored_default = "0"
class float_converter(CConverter):
type = 'float'
+ default_type = float
format_unit = 'f'
c_ignored_default = "0.0"
class double_converter(CConverter):
type = 'double'
+ default_type = float
format_unit = 'd'
c_ignored_default = "0.0"
class Py_complex_converter(CConverter):
type = 'Py_complex'
+ default_type = complex
format_unit = 'D'
c_ignored_default = "{0.0, 0.0}"
type = 'PyObject *'
format_unit = 'O'
- def converter_init(self, *, type=None, subclass_of=None):
- if subclass_of:
+ def converter_init(self, *, converter=None, type=None, subclass_of=None):
+ if converter:
+ if subclass_of:
+ fail("object: Cannot pass in both 'converter' and 'subclass_of'")
+ self.format_unit = 'O&'
+ self.converter = converter
+ elif subclass_of:
self.format_unit = 'O!'
self.subclass_of = subclass_of
+
if type is not None:
self.type = type
@add_legacy_c_converter('z#', nullable=True, length=True)
class str_converter(CConverter):
type = 'const char *'
+ default_type = (str, Null, NoneType)
format_unit = 's'
def converter_init(self, *, encoding=None, types="str",
class unicode_converter(CConverter):
type = 'PyObject *'
+ default_type = (str, Null, NoneType)
format_unit = 'U'
@add_legacy_c_converter('u#', length=True)
@add_legacy_c_converter('Z#', nullable=True, length=True)
class Py_UNICODE_converter(CConverter):
type = 'Py_UNICODE *'
+ default_type = (str, Null, NoneType)
format_unit = 'u'
def converter_init(self, *, nullable=False, length=False):
type = 'Py_buffer'
format_unit = 'y*'
impl_by_reference = True
- c_ignored_default = "{NULL, NULL, 0, 0, 0, 0, NULL, NULL, NULL, NULL, NULL}"
+ c_ignored_default = "{NULL, NULL}"
def converter_init(self, *, types='bytes bytearray buffer', nullable=False):
- if self.default != unspecified:
- fail("There is no legal default value for Py_buffer ")
+ if self.default not in (unspecified, None):
+ fail("The only legal default value for Py_buffer is None.")
self.c_default = self.c_ignored_default
types = set(types.strip().split())
bytes_type = set(('bytes',))
fail('Py_buffer_converter: illegal combination of arguments (nullable=True)')
elif types == (bytes_bytearray_buffer_type):
format_unit = 'y*'
- elif types == (bytearray_type | rwuffer_type):
+ elif types == (bytearray_type | rwbuffer_type):
format_unit = 'w*'
if not format_unit:
fail("Py_buffer_converter: illegal combination of arguments")
def cleanup(self):
name = ensure_legal_c_identifier(self.name)
- return "".join(["if (", name, ".buf)\n PyBuffer_Release(&", name, ");\n"])
+ return "".join(["if (", name, ".obj)\n PyBuffer_Release(&", name, ");\n"])
class self_converter(CConverter):
Py_INCREF(Py_None);
'''.strip())
-class int_return_converter(CReturnConverter):
+class bool_return_converter(CReturnConverter):
type = 'int'
def render(self, function, data):
self.declare(data)
self.err_occurred_if("_return_value == -1", data)
- data.return_conversion.append(
- 'return_value = PyLong_FromLong((long)_return_value);\n')
-
+ data.return_conversion.append('return_value = PyBool_FromLong((long)_return_value);\n')
class long_return_converter(CReturnConverter):
type = 'long'
+ conversion_fn = 'PyLong_FromLong'
+ cast = ''
def render(self, function, data):
self.declare(data)
self.err_occurred_if("_return_value == -1", data)
data.return_conversion.append(
- 'return_value = PyLong_FromLong(_return_value);\n')
+ ''.join(('return_value = ', self.conversion_fn, '(', self.cast, '_return_value);\n')))
+
+class int_return_converter(long_return_converter):
+ type = 'int'
+ cast = '(long)'
+class unsigned_long_return_converter(long_return_converter):
+ type = 'unsigned long'
+ conversion_fn = 'PyLong_FromUnsignedLong'
+
+class unsigned_int_return_converter(unsigned_long_return_converter):
+ type = 'unsigned int'
+ cast = '(unsigned long)'
-class Py_ssize_t_return_converter(CReturnConverter):
+class Py_ssize_t_return_converter(long_return_converter):
type = 'Py_ssize_t'
+ conversion_fn = 'PyLong_FromSsize_t'
+
+class size_t_return_converter(long_return_converter):
+ type = 'size_t'
+ conversion_fn = 'PyLong_FromSize_t'
+
+
+class double_return_converter(CReturnConverter):
+ type = 'double'
+ cast = ''
def render(self, function, data):
self.declare(data)
- self.err_occurred_if("_return_value == -1", data)
+ self.err_occurred_if("_return_value == -1.0", data)
data.return_conversion.append(
- 'return_value = PyLong_FromSsize_t(_return_value);\n')
+ 'return_value = PyFloat_FromDouble(' + self.cast + '_return_value);\n')
+
+class float_return_converter(double_return_converter):
+ type = 'float'
+ cast = '(double)'
class DecodeFSDefault_return_converter(CReturnConverter):
if isinstance(expr, ast.Name) and expr.id == 'NULL':
value = NULL
elif isinstance(expr, ast.Attribute):
+ c_default = kwargs.get("c_default")
+ if not (isinstance(c_default, str) and c_default):
+ fail("When you specify a named constant (" + repr(py_default) + ") as your default value,\nyou MUST specify a valid c_default.")
+
a = []
n = expr
while isinstance(n, ast.Attribute):
fail("Malformed default value (looked like a Python constant)")
a.append(n.id)
py_default = ".".join(reversed(a))
- value = None
- c_default = kwargs.get("c_default")
- if not (isinstance(c_default, str) and c_default):
- fail("When you specify a named constant (" + repr(py_default) + ") as your default value,\nyou MUST specify a valid c_default.")
kwargs["py_default"] = py_default
+ value = eval(py_default)
else:
value = ast.literal_eval(expr)
else:
if isinstance(annotation, ast.Name):
return annotation.id, False, {}
- assert isinstance(annotation, ast.Call)
+ if not isinstance(annotation, ast.Call):
+ fail("Annotations must be either a name, a function call, or a string.")
name = annotation.func.id
kwargs = {node.arg: ast.literal_eval(node.value) for node in annotation.keywords}
projects / python / commitdiff