Mirror
/
cpython
mirror of https://github.com/python/cpython
4
1
Fork 0
Code Issues Releases Wiki Activity

Close #24458: PEP 489 documentation 

Patch by Petr Viktorin.
This commit is contained in:
Nick Coghlan 2015-07-03 19:49:15 +10:00
parent ccc897f839
commit 2ab5b092e5
7 changed files with 306 additions and 98 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
Doc/c-api/init.rst
View File

@ -873,6 +873,8 @@ been created.
instead.
.. _sub-interpreter-support:
Sub-interpreter support
=======================

320
Doc/c-api/module.rst
View File

@ -82,6 +82,18 @@ Module Objects
Similar to :c:func:`PyModule_GetNameObject` but return the name encoded to
``'utf-8'``.
.. c:function:: void* PyModule_GetState(PyObject *module)
Return the "state" of the module, that is, a pointer to the block of memory
allocated at module creation time, or *NULL*. See
:c:member:`PyModuleDef.m_size`.
.. c:function:: PyModuleDef* PyModule_GetDef(PyObject *module)
Return a pointer to the :c:type:`PyModuleDef` struct from which the module was
created, or *NULL* if the module wasn't created from a definition.
.. c:function:: PyObject* PyModule_GetFilenameObject(PyObject *module)
@ -107,57 +119,25 @@ Module Objects
unencodable filenames, use :c:func:`PyModule_GetFilenameObject` instead.
Per-interpreter module state
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Single-phase initialization creates singleton modules that can store additional
information as part of the interpreter, allow that state to be retrieved later
with only a reference to the module definition, rather than to the module
itself.
.. c:function:: void* PyModule_GetState(PyObject *module)
Return the "state" of the module, that is, a pointer to the block of memory
allocated at module creation time, or *NULL*. See
:c:member:`PyModuleDef.m_size`.
.. c:function:: PyModuleDef* PyModule_GetDef(PyObject *module)
Return a pointer to the :c:type:`PyModuleDef` struct from which the module was
created, or *NULL* if the module wasn't created with
:c:func:`PyModule_Create`.
.. c:function:: PyObject* PyState_FindModule(PyModuleDef *def)
Returns the module object that was created from *def* for the current interpreter.
This method requires that the module object has been attached to the interpreter state with
:c:func:`PyState_AddModule` beforehand. In case the corresponding module object is not
found or has not been attached to the interpreter state yet, it returns NULL.
.. c:function:: int PyState_AddModule(PyObject *module, PyModuleDef *def)
Attaches the module object passed to the function to the interpreter state. This allows
the module object to be accessible via
:c:func:`PyState_FindModule`.
.. versionadded:: 3.3
.. c:function:: int PyState_RemoveModule(PyModuleDef *def)
Removes the module object created from *def* from the interpreter state.
.. versionadded:: 3.3
.. _initializing-modules:
Initializing C modules
^^^^^^^^^^^^^^^^^^^^^^
Modules objects are usually created from extension modules (shared libraries
which export an initialization function), or compiled-in modules
(where the initialization function is added using :c:func:`PyImport_AppendInittab`).
See :ref:`building` or :ref:`extending-with-embedding` for details.
The initialization function can either pass pass a module definition instance
to :c:func:`PyModule_Create`, and return the resulting module object,
or request "multi-phase initialization" by returning the definition struct itself.
.. c:type:: PyModuleDef
This struct holds all information that is needed to create a module object.
There is usually only one static variable of that type for each module, which
is statically initialized and then passed to :c:func:`PyModule_Create` in the
module initialization function.
The module definition struct, which holds all information needed to create
a module object. There is usually only one statically initialized variable
of this type for each module.
.. c:member:: PyModuleDef_Base m_base
@ -174,19 +154,21 @@ Initializing C modules
.. c:member:: Py_ssize_t m_size
Some modules allow re-initialization (calling their ``PyInit_*`` function
more than once). These modules should keep their state in a per-module
memory area that can be retrieved with :c:func:`PyModule_GetState`.
Module state may be kept in a per-module memory area that can be
retrieved with :c:func:`PyModule_GetState`, rather than in static globals.
This makes modules safe for use in multiple sub-interpreters.
This memory should be used, rather than static globals, to hold per-module
state, since it is then safe for use in multiple sub-interpreters. It is
freed when the module object is deallocated, after the :c:member:`m_free`
function has been called, if present.
This memory area is allocated based on *m_size* on module creation,
and freed when the module object is deallocated, after the
:c:member:`m_free` function has been called, if present.
Setting ``m_size`` to ``-1`` means that the module can not be
re-initialized because it has global state. Setting it to a non-negative
value means that the module can be re-initialized and specifies the
additional amount of memory it requires for its state.
Setting ``m_size`` to ``-1`` means that the module does not support
sub-interpreters, because it has global state.
Setting it to a non-negative value means that the module can be
re-initialized and specifies the additional amount of memory it requires
for its state. Non-negative ``m_size`` is required for multi-phase
initialization.
See :PEP:`3121` for more details.
@ -198,7 +180,15 @@ Initializing C modules
.. c:member:: PyModuleDef_Slot* m_slots
An array of slot definitions for multi-phase initialization, terminated by
a *NULL* entry.
a ``{0, NULL}`` entry.
When using single-phase initialization, *m_slots* must be *NULL*.
.. versionchanged:: 3.5
Prior to version 3.5, this member was always set to *NULL*,
and was defined as:
.. c:member:: inquiry m_reload
.. c:member:: traverseproc m_traverse
@ -215,20 +205,23 @@ Initializing C modules
A function to call during deallocation of the module object, or *NULL* if
not needed.
Single-phase initialization
...........................
The module initialization function may create and return the module object
directly. This is referred to as "single-phase initialization", and uses one
of the following two module creation functions:
.. c:function:: PyObject* PyModule_Create(PyModuleDef *module)
.. c:function:: PyObject* PyModule_Create(PyModuleDef *def)
Create a new module object, given the definition in *module*. This behaves
Create a new module object, given the definition in *def*. This behaves
like :c:func:`PyModule_Create2` with *module_api_version* set to
:const:`PYTHON_API_VERSION`.
.. c:function:: PyObject* PyModule_Create2(PyModuleDef *module, int module_api_version)
.. c:function:: PyObject* PyModule_Create2(PyModuleDef *def, int module_api_version)
Create a new module object, given the definition in *module*, assuming the
Create a new module object, given the definition in *def*, assuming the
API version *module_api_version*. If that version does not match the version
of the running interpreter, a :exc:`RuntimeWarning` is emitted.
@ -237,39 +230,179 @@ of the following two module creation functions:
Most uses of this function should be using :c:func:`PyModule_Create`
instead; only use this if you are sure you need it.
Before it is returned from in the initialization function, the resulting module
object is typically populated using functions like :c:func:`PyModule_AddObject`.
Alternatively, the module initialization function may instead return a
:c:type:`PyModuleDef` instance with a non-empty ``m_slots`` array. This is
referred to as "multi-phase initialization", and ``PyModuleDef`` instance
should be initialized with the following function:
.. _multi-phase-initialization:
.. c:function:: PyObject* PyModuleDef_Init(PyModuleDef *module)
Multi-phase initialization
..........................
An alternate way to specify extensions is to request "multi-phase initialization".
Extension modules created this way behave more like Python modules: the
initialization is split between the *creation phase*, when the module object
is created, and the *execution phase*, when it is populated.
The distinction is similar to the :py:meth:`__new__` and :py:meth:`__init__` methods
of classes.
Unlike modules created using single-phase initialization, these modules are not
singletons: if the *sys.modules* entry is removed and the module is re-imported,
a new module object is created, and the old module is subject to normal garbage
collection -- as with Python modules.
By default, multiple modules created from the same definition should be
independent: changes to one should not affect the others.
This means that all state should be specific to the module object (using e.g.
using :c:func:`PyModule_GetState`), or its contents (such as the module's
:attr:`__dict__` or individual classes created with :c:func:`PyType_FromSpec`).
All modules created using multi-phase initialization are expected to support
:ref:`sub-interpreters <sub-interpreter-support>`. Making sure multiple modules
are independent is typically enough to achieve this.
To request multi-phase initialization, the initialization function
(PyInit_modulename) returns a :c:type:`PyModuleDef` instance with non-empty
:c:member:`~PyModuleDef.m_slots`. Before it is returned, the ``PyModuleDef``
instance must be initialized with the following function:
.. c:function:: PyObject* PyModuleDef_Init(PyModuleDef *def)
Ensures a module definition is a properly initialized Python object that
correctly reports its type and reference count.
.. XXX (ncoghlan): It's not clear if it makes sense to document PyModule_ExecDef
PyModule_FromDefAndSpec or PyModule_FromDefAndSpec2 here, as end user code
generally shouldn't be calling those.
Returns *def* cast to ``PyObject*``, or *NULL* if an error occurred.
The module initialization function (if using single phase initialization) or
a function called from a module execution slot (if using multiphase
initialization), can use the following functions to help initialize the module
state:
.. versionadded:: 3.5
The *m_slots* member of the module definition must point to an array of
``PyModuleDef_Slot`` structures:
.. c:type:: PyModuleDef_Slot
.. c:member:: int slot
A slot ID, chosen from the available values explained below.
.. c:member:: void* value
Value of the slot, whose meaning depends on the slot ID.
.. versionadded:: 3.5
The *m_slots* array must be terminated by a slot with id 0.
The available slot types are:
.. c:var:: Py_mod_create
Specifies a function that is called to create the module object itself.
The *value* pointer of this slot must point to a function of the signature:
.. c:function:: PyObject* create_module(PyObject *spec, PyModuleDef *def)
The function receives a :py:class:`~importlib.machinery.ModuleSpec`
instance, as defined in :PEP:`451`, and the module definition.
It should return a new module object, or set an error
and return *NULL*.
This function should be kept minimal. In particular, it should not
call arbitrary Python code, as trying to import the same module again may
result in an infinite loop.
Multiple ``Py_mod_create`` slots may not be specified in one module
definition.
If ``Py_mod_create`` is not specified, the import machinery will create
a normal module object using :c:func:`PyModule_New`. The name is taken from
*spec*, not the definition, to allow extension modules to dynamically adjust
to their place in the module hierarchy and be imported under different
names through symlinks, all while sharing a single module definition.
There is no requirement for the returned object to be an instance of
:c:type:`PyModule_Type`. Any type can be used, as long as it supports
setting and getting import-related attributes.
However, only ``PyModule_Type`` instances may be returned if the
``PyModuleDef`` has non-*NULL* ``m_methods``, ``m_traverse``, ``m_clear``,
``m_free``; non-zero ``m_size``; or slots other than ``Py_mod_create``.
.. c:var:: Py_mod_exec
Specifies a function that is called to *execute* the module.
This is equivalent to executing the code of a Python module: typically,
this function adds classes and constants to the module.
The signature of the function is:
.. c:function:: int exec_module(PyObject* module)
If multiple ``Py_mod_exec`` slots are specified, they are processed in the
order they appear in the *m_slots* array.
See :PEP:`489` for more details on multi-phase initialization.
Low-level module creation functions
...................................
The following functions are called under the hood when using multi-phase
initialization. They can be used directly, for example when creating module
objects dynamically. Note that both ``PyModule_FromDefAndSpec`` and
``PyModule_ExecDef`` must be called to fully initialize a module.
.. c:function:: PyObject * PyModule_FromDefAndSpec(PyModuleDef *def, PyObject *spec)
Create a new module object, given the definition in *module* and the
ModuleSpec *spec*. This behaves like :c:func:`PyModule_FromDefAndSpec2`
with *module_api_version* set to :const:`PYTHON_API_VERSION`.
.. versionadded:: 3.5
.. c:function:: PyObject * PyModule_FromDefAndSpec2(PyModuleDef *def, PyObject *spec, int module_api_version)
Create a new module object, given the definition in *module* and the
ModuleSpec *spec*, assuming the API version *module_api_version*.
If that version does not match the version of the running interpreter,
a :exc:`RuntimeWarning` is emitted.
.. note::
Most uses of this function should be using :c:func:`PyModule_FromDefAndSpec`
instead; only use this if you are sure you need it.
.. versionadded:: 3.5
.. c:function:: int PyModule_ExecDef(PyObject *module, PyModuleDef *def)
Process any execution slots (:c:data:`Py_mod_exec`) given in *def*.
.. versionadded:: 3.5
.. c:function:: int PyModule_SetDocString(PyObject *module, const char *docstring)
Set the docstring for *module* to *docstring*. Return ``-1`` on error, ``0``
on success.
Set the docstring for *module* to *docstring*.
This function is called automatically when creating a module from
``PyModuleDef``, using either ``PyModule_Create`` or
``PyModule_FromDefAndSpec``.
.. versionadded:: 3.5
.. c:function:: int PyModule_AddFunctions(PyObject *module, PyMethodDef *functions)
Add the functions from the ``NULL`` terminated *functions* array to *module*.
Add the functions from the *NULL* terminated *functions* array to *module*.
Refer to the :c:type:`PyMethodDef` documentation for details on individual
entries (due to the lack of a shared module namespace, module level
"functions" implemented in C typically receive the module as their first
parameter, making them similar to instance methods on Python classes).
This function is called automatically when creating a module from
``PyModuleDef``, using either ``PyModule_Create`` or
``PyModule_FromDefAndSpec``.
.. versionadded:: 3.5
Support functions
.................
The module initialization function (if using single phase initialization) or
a function called from a module execution slot (if using multi-phase
initialization), can use the following functions to help initialize the module
state:
.. c:function:: int PyModule_AddObject(PyObject *module, const char *name, PyObject *value)
@ -288,7 +421,7 @@ state:
Add a string constant to *module* as *name*. This convenience function can be
used from the module's initialization function. The string *value* must be
null-terminated. Return ``-1`` on error, ``0`` on success.
*NULL*-terminated. Return ``-1`` on error, ``0`` on success.
.. c:function:: int PyModule_AddIntMacro(PyObject *module, macro)
@ -302,3 +435,36 @@ state:
.. c:function:: int PyModule_AddStringMacro(PyObject *module, macro)
Add a string constant to *module*.
Module lookup
^^^^^^^^^^^^^
Single-phase initialization creates singleton modules that can be looked up
in the context of the current interpreter. This allows the module object to be
retrieved later with only a reference to the module definition.
These functions will not work on modules created using multi-phase initialization,
since multiple such modules can be created from a single definition.
.. c:function:: PyObject* PyState_FindModule(PyModuleDef *def)
Returns the module object that was created from *def* for the current interpreter.
This method requires that the module object has been attached to the interpreter state with
:c:func:`PyState_AddModule` beforehand. In case the corresponding module object is not
found or has not been attached to the interpreter state yet, it returns *NULL*.
.. c:function:: int PyState_AddModule(PyObject *module, PyModuleDef *def)
Attaches the module object passed to the function to the interpreter state. This allows
the module object to be accessible via :c:func:`PyState_FindModule`.
Only effective on modules created using single-phase initialization.
.. versionadded:: 3.3
.. c:function:: int PyState_RemoveModule(PyModuleDef *def)
Removes the module object created from *def* from the interpreter state.
.. versionadded:: 3.3

63
Doc/extending/building.rst
View File

@ -1,27 +1,58 @@
.. highlightlang:: c
.. _building:
********************************************
*****************************
Building C and C++ Extensions
*****************************
A C extension for CPython is a shared library (e.g. a ``.so`` file on Linux,
``.pyd`` on Windows), which exports an *initialization function*.
To be importable, the shared library must be available on :envvar:`PYTHONPATH`,
and must be named after the module name, with an appropriate extension.
When using distutils, the correct filename is generated automatically.
The initialization function has the signature:
.. c:function:: PyObject* PyInit_modulename(void)
It returns either a fully-initialized module, or a :c:type:`PyModuleDef`
instance. See :ref:`initializing-modules` for details.
.. highlightlang:: python
For modules with ASCII-only names, the function must be named
``PyInit_<modulename>``, with ``<modulename>`` replaced by the name of the
module. When using :ref:`multi-phase-initialization`, non-ASCII module names
are allowed. In this case, the initialization function name is
``PyInitU_<modulename>``, with ``<modulename>`` encoded using Python's
*punycode* encoding with hyphens replaced by underscores. In Python::
def initfunc_name(name):
try:
suffix = b'_' + name.encode('ascii')
except UnicodeEncodeError:
suffix = b'U_' + name.encode('punycode').replace(b'-', b'_')
return b'PyInit' + suffix
It is possible to export multiple modules from a single shared library by
defining multiple initialization functions. However, importing them requires
using symbolic links or a custom importer, because by default only the
function corresponding to the filename is found.
See :PEP:`489#multiple-modules-in-one-library` for details.
.. highlightlang:: c
Building C and C++ Extensions with distutils
********************************************
============================================
.. sectionauthor:: Martin v. Löwis <martin@v.loewis.de>
Starting in Python 1.4, Python provides, on Unix, a special make file for
building make files for building dynamically-linked extensions and custom
interpreters. Starting with Python 2.0, this mechanism (known as related to
Makefile.pre.in, and Setup files) is no longer supported. Building custom
interpreters was rarely used, and extension modules can be built using
distutils.
Building an extension module using distutils requires that distutils is
installed on the build machine, which is included in Python 2.x and available
separately for Python 1.5. Since distutils also supports creation of binary
packages, users don't necessarily need a compiler and distutils to install the
extension.
Extension modules can be built using distutils, which is included in Python.
Since distutils also supports creation of binary packages, users don't
necessarily need a compiler and distutils to install the extension.
A distutils package contains a driver script, :file:`setup.py`. This is a plain
Python file, which, in the most simple case, could look like this::

7
Doc/extending/extending.rst
View File

@ -413,6 +413,13 @@ A more substantial example module is included in the Python source distribution
as :file:`Modules/xxmodule.c`. This file may be used as a template or simply
read as an example.
.. note::
Unlike our ``spam`` example, ``xxmodule`` uses *multi-phase initialization*
(new in Python 3.5), where a PyModuleDef structure is returned from
``PyInit_spam``, and creation of the module is left to the import machinery.
For details on multi-phase initialization, see :PEP:`489`.
.. _compilation:

5
Doc/extending/windows.rst
View File

@ -98,9 +98,8 @@ described here are distributed with the Python sources in the
it. Copy your C sources into it. Note that the module source file name does
not necessarily have to match the module name, but the name of the
initialization function should match the module name --- you can only import a
module :mod:`spam` if its initialization function is called :c:func:`initspam`,
and it should call :c:func:`Py_InitModule` with the string ``"spam"`` as its
first argument (use the minimal :file:`example.c` in this directory as a guide).
module :mod:`spam` if its initialization function is called :c:func:`PyInit_spam`,
(see :ref:`building`, or use the minimal :file:`Modules/xxmodule.c` 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
:file:`spam_d.pyd` (in Debug mode). The extension :file:`.pyd` was chosen

4
Doc/whatsnew/3.5.rst
View File

@ -283,7 +283,7 @@ two step module loading mechanism introduced by :pep:`451` in Python 3.4.
This change brings the import semantics of extension modules that opt-in to
using the new mechanism much closer to those of Python source and bytecode
modules, including the ability to any valid identifier as a module name,
modules, including the ability to use any valid identifier as a module name,
rather than being restricted to ASCII.
.. seealso::
@ -763,7 +763,7 @@ unicodedata
-----------
* The :mod:`unicodedata` module now uses data from `Unicode 8.0.0
<http://unicode.org/versions/Unicode8.0.0/>`_.
<http://unicode.org/versions/Unicode8.0.0/>`_.
wsgiref

3
Misc/NEWS
View File

@ -92,6 +92,9 @@ Tests
Documentation
-------------
- Issue #24458: Update documentation to cover multi-phase initialization for
extension modules (PEP 489). Patch by Petr Viktorin.
- Issue #24351: Clarify what is meant by "identifier" in the context of
string.Template instances.