cpython/Doc/howto/cporting.rst

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Devil merge! Merged revisions 66561,66564,66580,66610,66614,66618,66624-66625,66628-66629,66643,66645,66660-66665 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r66561 | benjamin.peterson | 2008-09-22 17:13:29 -0500 (Mon, 22 Sep 2008) | 1 line clean up docs for platform's linux_distribution and dist functions ........ r66564 | benjamin.peterson | 2008-09-23 08:32:46 -0500 (Tue, 23 Sep 2008) | 1 line mention how to override boolean evaluation ........ r66580 | georg.brandl | 2008-09-24 04:47:55 -0500 (Wed, 24 Sep 2008) | 2 lines Indentation normalization. ........ r66610 | andrew.kuchling | 2008-09-24 12:27:55 -0500 (Wed, 24 Sep 2008) | 1 line Improve wording ........ r66614 | benjamin.peterson | 2008-09-24 17:11:59 -0500 (Wed, 24 Sep 2008) | 4 lines #3950 fix missing scale factors in turtle.py reviewers: Georg, Benjamin ........ r66618 | benjamin.peterson | 2008-09-25 15:35:45 -0500 (Thu, 25 Sep 2008) | 1 line add a NEWs entry for r66614 ........ r66624 | raymond.hettinger | 2008-09-25 18:31:52 -0500 (Thu, 25 Sep 2008) | 1 line Fix namedtuple bug reported by Glenn Linderman. Template did not form correctly if the field names were input in Unicode. ........ r66625 | benjamin.peterson | 2008-09-25 21:58:36 -0500 (Thu, 25 Sep 2008) | 1 line add the beginnings of a C-API 2 -> 3 porting guide ........ r66628 | benjamin.peterson | 2008-09-26 15:52:06 -0500 (Fri, 26 Sep 2008) | 1 line add an 'other options' section ........ r66629 | georg.brandl | 2008-09-26 16:15:21 -0500 (Fri, 26 Sep 2008) | 2 lines typos. ........ r66643 | andrew.kuchling | 2008-09-27 09:12:33 -0500 (Sat, 27 Sep 2008) | 1 line Add a last bunch of items ........ r66645 | benjamin.peterson | 2008-09-27 11:23:55 -0500 (Sat, 27 Sep 2008) | 1 line 2to3's api should be considered unstable ........ r66660 | andrew.kuchling | 2008-09-27 17:54:08 -0500 (Sat, 27 Sep 2008) | 1 line #3510: future-proof text ........ r66661 | benjamin.peterson | 2008-09-27 18:28:43 -0500 (Sat, 27 Sep 2008) | 1 line clarify a few things ........ r66662 | andrew.kuchling | 2008-09-27 19:15:27 -0500 (Sat, 27 Sep 2008) | 1 line #1579477: mention necessity to flush output before exec'ing ........ r66663 | andrew.kuchling | 2008-09-27 20:08:47 -0500 (Sat, 27 Sep 2008) | 1 line #1415508: Document two functions ........ r66664 | benjamin.peterson | 2008-09-27 20:51:36 -0500 (Sat, 27 Sep 2008) | 1 line better grammar ........ r66665 | benjamin.peterson | 2008-09-27 20:53:29 -0500 (Sat, 27 Sep 2008) | 1 line note the 2to3 -d could be useful for other refactoring ........
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.. highlightlang:: c
.. _cporting-howto:
*************************************
Porting Extension Modules to Python 3
*************************************
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:author: Benjamin Peterson
.. topic:: Abstract
Although changing the C-API was not one of Python 3's objectives,
the many Python-level changes made leaving Python 2's API intact
impossible. In fact, some changes such as :func:`int` and
:func:`long` unification are more obvious on the C level. This
document endeavors to document incompatibilities and how they can
be worked around.
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Conditional compilation
=======================
The easiest way to compile only some code for Python 3 is to check
if :c:macro:`PY_MAJOR_VERSION` is greater than or equal to 3. ::
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#if PY_MAJOR_VERSION >= 3
#define IS_PY3K
#endif
API functions that are not present can be aliased to their equivalents within
conditional blocks.
Changes to Object APIs
======================
Python 3 merged together some types with similar functions while cleanly
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separating others.
str/unicode Unification
-----------------------
Python 3's :func:`str` type is equivalent to Python 2's :func:`unicode`; the C
functions are called ``PyUnicode_*`` for both. The old 8-bit string type has become
:func:`bytes`, with C functions called ``PyBytes_*``. Python 2.6 and later provide a compatibility header,
Devil merge! Merged revisions 66561,66564,66580,66610,66614,66618,66624-66625,66628-66629,66643,66645,66660-66665 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r66561 | benjamin.peterson | 2008-09-22 17:13:29 -0500 (Mon, 22 Sep 2008) | 1 line clean up docs for platform's linux_distribution and dist functions ........ r66564 | benjamin.peterson | 2008-09-23 08:32:46 -0500 (Tue, 23 Sep 2008) | 1 line mention how to override boolean evaluation ........ r66580 | georg.brandl | 2008-09-24 04:47:55 -0500 (Wed, 24 Sep 2008) | 2 lines Indentation normalization. ........ r66610 | andrew.kuchling | 2008-09-24 12:27:55 -0500 (Wed, 24 Sep 2008) | 1 line Improve wording ........ r66614 | benjamin.peterson | 2008-09-24 17:11:59 -0500 (Wed, 24 Sep 2008) | 4 lines #3950 fix missing scale factors in turtle.py reviewers: Georg, Benjamin ........ r66618 | benjamin.peterson | 2008-09-25 15:35:45 -0500 (Thu, 25 Sep 2008) | 1 line add a NEWs entry for r66614 ........ r66624 | raymond.hettinger | 2008-09-25 18:31:52 -0500 (Thu, 25 Sep 2008) | 1 line Fix namedtuple bug reported by Glenn Linderman. Template did not form correctly if the field names were input in Unicode. ........ r66625 | benjamin.peterson | 2008-09-25 21:58:36 -0500 (Thu, 25 Sep 2008) | 1 line add the beginnings of a C-API 2 -> 3 porting guide ........ r66628 | benjamin.peterson | 2008-09-26 15:52:06 -0500 (Fri, 26 Sep 2008) | 1 line add an 'other options' section ........ r66629 | georg.brandl | 2008-09-26 16:15:21 -0500 (Fri, 26 Sep 2008) | 2 lines typos. ........ r66643 | andrew.kuchling | 2008-09-27 09:12:33 -0500 (Sat, 27 Sep 2008) | 1 line Add a last bunch of items ........ r66645 | benjamin.peterson | 2008-09-27 11:23:55 -0500 (Sat, 27 Sep 2008) | 1 line 2to3's api should be considered unstable ........ r66660 | andrew.kuchling | 2008-09-27 17:54:08 -0500 (Sat, 27 Sep 2008) | 1 line #3510: future-proof text ........ r66661 | benjamin.peterson | 2008-09-27 18:28:43 -0500 (Sat, 27 Sep 2008) | 1 line clarify a few things ........ r66662 | andrew.kuchling | 2008-09-27 19:15:27 -0500 (Sat, 27 Sep 2008) | 1 line #1579477: mention necessity to flush output before exec'ing ........ r66663 | andrew.kuchling | 2008-09-27 20:08:47 -0500 (Sat, 27 Sep 2008) | 1 line #1415508: Document two functions ........ r66664 | benjamin.peterson | 2008-09-27 20:51:36 -0500 (Sat, 27 Sep 2008) | 1 line better grammar ........ r66665 | benjamin.peterson | 2008-09-27 20:53:29 -0500 (Sat, 27 Sep 2008) | 1 line note the 2to3 -d could be useful for other refactoring ........
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:file:`bytesobject.h`, mapping ``PyBytes`` names to ``PyString`` ones. For best
compatibility with Python 3, :c:type:`PyUnicode` should be used for textual data and
:c:type:`PyBytes` for binary data. It's also important to remember that
:c:type:`PyBytes` and :c:type:`PyUnicode` in Python 3 are not interchangeable like
:c:type:`PyString` and :c:type:`PyUnicode` are in Python 2. The following example
2010-10-06 07:26:05 -03:00
shows best practices with regards to :c:type:`PyUnicode`, :c:type:`PyString`,
and :c:type:`PyBytes`. ::
Devil merge! Merged revisions 66561,66564,66580,66610,66614,66618,66624-66625,66628-66629,66643,66645,66660-66665 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r66561 | benjamin.peterson | 2008-09-22 17:13:29 -0500 (Mon, 22 Sep 2008) | 1 line clean up docs for platform's linux_distribution and dist functions ........ r66564 | benjamin.peterson | 2008-09-23 08:32:46 -0500 (Tue, 23 Sep 2008) | 1 line mention how to override boolean evaluation ........ r66580 | georg.brandl | 2008-09-24 04:47:55 -0500 (Wed, 24 Sep 2008) | 2 lines Indentation normalization. ........ r66610 | andrew.kuchling | 2008-09-24 12:27:55 -0500 (Wed, 24 Sep 2008) | 1 line Improve wording ........ r66614 | benjamin.peterson | 2008-09-24 17:11:59 -0500 (Wed, 24 Sep 2008) | 4 lines #3950 fix missing scale factors in turtle.py reviewers: Georg, Benjamin ........ r66618 | benjamin.peterson | 2008-09-25 15:35:45 -0500 (Thu, 25 Sep 2008) | 1 line add a NEWs entry for r66614 ........ r66624 | raymond.hettinger | 2008-09-25 18:31:52 -0500 (Thu, 25 Sep 2008) | 1 line Fix namedtuple bug reported by Glenn Linderman. Template did not form correctly if the field names were input in Unicode. ........ r66625 | benjamin.peterson | 2008-09-25 21:58:36 -0500 (Thu, 25 Sep 2008) | 1 line add the beginnings of a C-API 2 -> 3 porting guide ........ r66628 | benjamin.peterson | 2008-09-26 15:52:06 -0500 (Fri, 26 Sep 2008) | 1 line add an 'other options' section ........ r66629 | georg.brandl | 2008-09-26 16:15:21 -0500 (Fri, 26 Sep 2008) | 2 lines typos. ........ r66643 | andrew.kuchling | 2008-09-27 09:12:33 -0500 (Sat, 27 Sep 2008) | 1 line Add a last bunch of items ........ r66645 | benjamin.peterson | 2008-09-27 11:23:55 -0500 (Sat, 27 Sep 2008) | 1 line 2to3's api should be considered unstable ........ r66660 | andrew.kuchling | 2008-09-27 17:54:08 -0500 (Sat, 27 Sep 2008) | 1 line #3510: future-proof text ........ r66661 | benjamin.peterson | 2008-09-27 18:28:43 -0500 (Sat, 27 Sep 2008) | 1 line clarify a few things ........ r66662 | andrew.kuchling | 2008-09-27 19:15:27 -0500 (Sat, 27 Sep 2008) | 1 line #1579477: mention necessity to flush output before exec'ing ........ r66663 | andrew.kuchling | 2008-09-27 20:08:47 -0500 (Sat, 27 Sep 2008) | 1 line #1415508: Document two functions ........ r66664 | benjamin.peterson | 2008-09-27 20:51:36 -0500 (Sat, 27 Sep 2008) | 1 line better grammar ........ r66665 | benjamin.peterson | 2008-09-27 20:53:29 -0500 (Sat, 27 Sep 2008) | 1 line note the 2to3 -d could be useful for other refactoring ........
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#include "stdlib.h"
#include "Python.h"
#include "bytesobject.h"
/* text example */
static PyObject *
say_hello(PyObject *self, PyObject *args) {
PyObject *name, *result;
if (!PyArg_ParseTuple(args, "U:say_hello", &name))
return NULL;
result = PyUnicode_FromFormat("Hello, %S!", name);
return result;
}
/* just a forward */
static char * do_encode(PyObject *);
/* bytes example */
static PyObject *
encode_object(PyObject *self, PyObject *args) {
char *encoded;
PyObject *result, *myobj;
if (!PyArg_ParseTuple(args, "O:encode_object", &myobj))
return NULL;
encoded = do_encode(myobj);
if (encoded == NULL)
return NULL;
result = PyBytes_FromString(encoded);
free(encoded);
return result;
}
long/int Unification
--------------------
Python 3 has only one integer type, :func:`int`. But it actually
corresponds to Python 2's :func:`long` type—the :func:`int` type
used in Python 2 was removed. In the C-API, ``PyInt_*`` functions
are replaced by their ``PyLong_*`` equivalents.
Devil merge! Merged revisions 66561,66564,66580,66610,66614,66618,66624-66625,66628-66629,66643,66645,66660-66665 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r66561 | benjamin.peterson | 2008-09-22 17:13:29 -0500 (Mon, 22 Sep 2008) | 1 line clean up docs for platform's linux_distribution and dist functions ........ r66564 | benjamin.peterson | 2008-09-23 08:32:46 -0500 (Tue, 23 Sep 2008) | 1 line mention how to override boolean evaluation ........ r66580 | georg.brandl | 2008-09-24 04:47:55 -0500 (Wed, 24 Sep 2008) | 2 lines Indentation normalization. ........ r66610 | andrew.kuchling | 2008-09-24 12:27:55 -0500 (Wed, 24 Sep 2008) | 1 line Improve wording ........ r66614 | benjamin.peterson | 2008-09-24 17:11:59 -0500 (Wed, 24 Sep 2008) | 4 lines #3950 fix missing scale factors in turtle.py reviewers: Georg, Benjamin ........ r66618 | benjamin.peterson | 2008-09-25 15:35:45 -0500 (Thu, 25 Sep 2008) | 1 line add a NEWs entry for r66614 ........ r66624 | raymond.hettinger | 2008-09-25 18:31:52 -0500 (Thu, 25 Sep 2008) | 1 line Fix namedtuple bug reported by Glenn Linderman. Template did not form correctly if the field names were input in Unicode. ........ r66625 | benjamin.peterson | 2008-09-25 21:58:36 -0500 (Thu, 25 Sep 2008) | 1 line add the beginnings of a C-API 2 -> 3 porting guide ........ r66628 | benjamin.peterson | 2008-09-26 15:52:06 -0500 (Fri, 26 Sep 2008) | 1 line add an 'other options' section ........ r66629 | georg.brandl | 2008-09-26 16:15:21 -0500 (Fri, 26 Sep 2008) | 2 lines typos. ........ r66643 | andrew.kuchling | 2008-09-27 09:12:33 -0500 (Sat, 27 Sep 2008) | 1 line Add a last bunch of items ........ r66645 | benjamin.peterson | 2008-09-27 11:23:55 -0500 (Sat, 27 Sep 2008) | 1 line 2to3's api should be considered unstable ........ r66660 | andrew.kuchling | 2008-09-27 17:54:08 -0500 (Sat, 27 Sep 2008) | 1 line #3510: future-proof text ........ r66661 | benjamin.peterson | 2008-09-27 18:28:43 -0500 (Sat, 27 Sep 2008) | 1 line clarify a few things ........ r66662 | andrew.kuchling | 2008-09-27 19:15:27 -0500 (Sat, 27 Sep 2008) | 1 line #1579477: mention necessity to flush output before exec'ing ........ r66663 | andrew.kuchling | 2008-09-27 20:08:47 -0500 (Sat, 27 Sep 2008) | 1 line #1415508: Document two functions ........ r66664 | benjamin.peterson | 2008-09-27 20:51:36 -0500 (Sat, 27 Sep 2008) | 1 line better grammar ........ r66665 | benjamin.peterson | 2008-09-27 20:53:29 -0500 (Sat, 27 Sep 2008) | 1 line note the 2to3 -d could be useful for other refactoring ........
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Module initialization and state
===============================
Python 3 has a revamped extension module initialization system. (See
:pep:`3121`.) Instead of storing module state in globals, they should
be stored in an interpreter specific structure. Creating modules that
act correctly in both Python 2 and Python 3 is tricky. The following
simple example demonstrates how. ::
Devil merge! Merged revisions 66561,66564,66580,66610,66614,66618,66624-66625,66628-66629,66643,66645,66660-66665 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r66561 | benjamin.peterson | 2008-09-22 17:13:29 -0500 (Mon, 22 Sep 2008) | 1 line clean up docs for platform's linux_distribution and dist functions ........ r66564 | benjamin.peterson | 2008-09-23 08:32:46 -0500 (Tue, 23 Sep 2008) | 1 line mention how to override boolean evaluation ........ r66580 | georg.brandl | 2008-09-24 04:47:55 -0500 (Wed, 24 Sep 2008) | 2 lines Indentation normalization. ........ r66610 | andrew.kuchling | 2008-09-24 12:27:55 -0500 (Wed, 24 Sep 2008) | 1 line Improve wording ........ r66614 | benjamin.peterson | 2008-09-24 17:11:59 -0500 (Wed, 24 Sep 2008) | 4 lines #3950 fix missing scale factors in turtle.py reviewers: Georg, Benjamin ........ r66618 | benjamin.peterson | 2008-09-25 15:35:45 -0500 (Thu, 25 Sep 2008) | 1 line add a NEWs entry for r66614 ........ r66624 | raymond.hettinger | 2008-09-25 18:31:52 -0500 (Thu, 25 Sep 2008) | 1 line Fix namedtuple bug reported by Glenn Linderman. Template did not form correctly if the field names were input in Unicode. ........ r66625 | benjamin.peterson | 2008-09-25 21:58:36 -0500 (Thu, 25 Sep 2008) | 1 line add the beginnings of a C-API 2 -> 3 porting guide ........ r66628 | benjamin.peterson | 2008-09-26 15:52:06 -0500 (Fri, 26 Sep 2008) | 1 line add an 'other options' section ........ r66629 | georg.brandl | 2008-09-26 16:15:21 -0500 (Fri, 26 Sep 2008) | 2 lines typos. ........ r66643 | andrew.kuchling | 2008-09-27 09:12:33 -0500 (Sat, 27 Sep 2008) | 1 line Add a last bunch of items ........ r66645 | benjamin.peterson | 2008-09-27 11:23:55 -0500 (Sat, 27 Sep 2008) | 1 line 2to3's api should be considered unstable ........ r66660 | andrew.kuchling | 2008-09-27 17:54:08 -0500 (Sat, 27 Sep 2008) | 1 line #3510: future-proof text ........ r66661 | benjamin.peterson | 2008-09-27 18:28:43 -0500 (Sat, 27 Sep 2008) | 1 line clarify a few things ........ r66662 | andrew.kuchling | 2008-09-27 19:15:27 -0500 (Sat, 27 Sep 2008) | 1 line #1579477: mention necessity to flush output before exec'ing ........ r66663 | andrew.kuchling | 2008-09-27 20:08:47 -0500 (Sat, 27 Sep 2008) | 1 line #1415508: Document two functions ........ r66664 | benjamin.peterson | 2008-09-27 20:51:36 -0500 (Sat, 27 Sep 2008) | 1 line better grammar ........ r66665 | benjamin.peterson | 2008-09-27 20:53:29 -0500 (Sat, 27 Sep 2008) | 1 line note the 2to3 -d could be useful for other refactoring ........
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#include "Python.h"
struct module_state {
PyObject *error;
};
#if PY_MAJOR_VERSION >= 3
#define GETSTATE(m) ((struct module_state*)PyModule_GetState(m))
#else
#define GETSTATE(m) (&_state)
static struct module_state _state;
#endif
static PyObject *
error_out(PyObject *m) {
struct module_state *st = GETSTATE(m);
PyErr_SetString(st->error, "something bad happened");
return NULL;
}
static PyMethodDef myextension_methods[] = {
{"error_out", (PyCFunction)error_out, METH_NOARGS, NULL},
{NULL, NULL}
};
#if PY_MAJOR_VERSION >= 3
static int myextension_traverse(PyObject *m, visitproc visit, void *arg) {
Py_VISIT(GETSTATE(m)->error);
return 0;
}
static int myextension_clear(PyObject *m) {
Py_CLEAR(GETSTATE(m)->error);
return 0;
}
static struct PyModuleDef moduledef = {
PyModuleDef_HEAD_INIT,
"myextension",
NULL,
sizeof(struct module_state),
myextension_methods,
NULL,
myextension_traverse,
myextension_clear,
NULL
};
#define INITERROR return NULL
PyMODINIT_FUNC
Devil merge! Merged revisions 66561,66564,66580,66610,66614,66618,66624-66625,66628-66629,66643,66645,66660-66665 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r66561 | benjamin.peterson | 2008-09-22 17:13:29 -0500 (Mon, 22 Sep 2008) | 1 line clean up docs for platform's linux_distribution and dist functions ........ r66564 | benjamin.peterson | 2008-09-23 08:32:46 -0500 (Tue, 23 Sep 2008) | 1 line mention how to override boolean evaluation ........ r66580 | georg.brandl | 2008-09-24 04:47:55 -0500 (Wed, 24 Sep 2008) | 2 lines Indentation normalization. ........ r66610 | andrew.kuchling | 2008-09-24 12:27:55 -0500 (Wed, 24 Sep 2008) | 1 line Improve wording ........ r66614 | benjamin.peterson | 2008-09-24 17:11:59 -0500 (Wed, 24 Sep 2008) | 4 lines #3950 fix missing scale factors in turtle.py reviewers: Georg, Benjamin ........ r66618 | benjamin.peterson | 2008-09-25 15:35:45 -0500 (Thu, 25 Sep 2008) | 1 line add a NEWs entry for r66614 ........ r66624 | raymond.hettinger | 2008-09-25 18:31:52 -0500 (Thu, 25 Sep 2008) | 1 line Fix namedtuple bug reported by Glenn Linderman. Template did not form correctly if the field names were input in Unicode. ........ r66625 | benjamin.peterson | 2008-09-25 21:58:36 -0500 (Thu, 25 Sep 2008) | 1 line add the beginnings of a C-API 2 -> 3 porting guide ........ r66628 | benjamin.peterson | 2008-09-26 15:52:06 -0500 (Fri, 26 Sep 2008) | 1 line add an 'other options' section ........ r66629 | georg.brandl | 2008-09-26 16:15:21 -0500 (Fri, 26 Sep 2008) | 2 lines typos. ........ r66643 | andrew.kuchling | 2008-09-27 09:12:33 -0500 (Sat, 27 Sep 2008) | 1 line Add a last bunch of items ........ r66645 | benjamin.peterson | 2008-09-27 11:23:55 -0500 (Sat, 27 Sep 2008) | 1 line 2to3's api should be considered unstable ........ r66660 | andrew.kuchling | 2008-09-27 17:54:08 -0500 (Sat, 27 Sep 2008) | 1 line #3510: future-proof text ........ r66661 | benjamin.peterson | 2008-09-27 18:28:43 -0500 (Sat, 27 Sep 2008) | 1 line clarify a few things ........ r66662 | andrew.kuchling | 2008-09-27 19:15:27 -0500 (Sat, 27 Sep 2008) | 1 line #1579477: mention necessity to flush output before exec'ing ........ r66663 | andrew.kuchling | 2008-09-27 20:08:47 -0500 (Sat, 27 Sep 2008) | 1 line #1415508: Document two functions ........ r66664 | benjamin.peterson | 2008-09-27 20:51:36 -0500 (Sat, 27 Sep 2008) | 1 line better grammar ........ r66665 | benjamin.peterson | 2008-09-27 20:53:29 -0500 (Sat, 27 Sep 2008) | 1 line note the 2to3 -d could be useful for other refactoring ........
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PyInit_myextension(void)
#else
#define INITERROR return
void
initmyextension(void)
#endif
{
#if PY_MAJOR_VERSION >= 3
PyObject *module = PyModule_Create(&moduledef);
#else
PyObject *module = Py_InitModule("myextension", myextension_methods);
#endif
if (module == NULL)
INITERROR;
struct module_state *st = GETSTATE(module);
st->error = PyErr_NewException("myextension.Error", NULL, NULL);
if (st->error == NULL) {
Py_DECREF(module);
INITERROR;
}
#if PY_MAJOR_VERSION >= 3
return module;
#endif
}
CObject replaced with Capsule
=============================
The :c:type:`Capsule` object was introduced in Python 3.1 and 2.7 to replace
:c:type:`CObject`. CObjects were useful,
but the :c:type:`CObject` API was problematic: it didn't permit distinguishing
between valid CObjects, which allowed mismatched CObjects to crash the
interpreter, and some of its APIs relied on undefined behavior in C.
(For further reading on the rationale behind Capsules, please see :issue:`5630`.)
If you're currently using CObjects, and you want to migrate to 3.1 or newer,
you'll need to switch to Capsules.
:c:type:`CObject` was deprecated in 3.1 and 2.7 and completely removed in
Python 3.2. If you only support 2.7, or 3.1 and above, you
can simply switch to :c:type:`Capsule`. If you need to support Python 3.0,
or versions of Python earlier than 2.7,
you'll have to support both CObjects and Capsules.
(Note that Python 3.0 is no longer supported, and it is not recommended
for production use.)
The following example header file :file:`capsulethunk.h` may
solve the problem for you. Simply write your code against the
:c:type:`Capsule` API and include this header file after
:file:`Python.h`. Your code will automatically use Capsules
in versions of Python with Capsules, and switch to CObjects
when Capsules are unavailable.
:file:`capsulethunk.h` simulates Capsules using CObjects. However,
:c:type:`CObject` provides no place to store the capsule's "name". As a
result the simulated :c:type:`Capsule` objects created by :file:`capsulethunk.h`
behave slightly differently from real Capsules. Specifically:
* The name parameter passed in to :c:func:`PyCapsule_New` is ignored.
* The name parameter passed in to :c:func:`PyCapsule_IsValid` and
:c:func:`PyCapsule_GetPointer` is ignored, and no error checking
of the name is performed.
* :c:func:`PyCapsule_GetName` always returns NULL.
* :c:func:`PyCapsule_SetName` always raises an exception and
returns failure. (Since there's no way to store a name
in a CObject, noisy failure of :c:func:`PyCapsule_SetName`
was deemed preferable to silent failure here. If this is
2012-03-24 13:39:57 -03:00
inconvenient, feel free to modify your local
copy as you see fit.)
You can find :file:`capsulethunk.h` in the Python source distribution
as :source:`Doc/includes/capsulethunk.h`. We also include it here for
your convenience:
.. literalinclude:: ../includes/capsulethunk.h
Devil merge! Merged revisions 66561,66564,66580,66610,66614,66618,66624-66625,66628-66629,66643,66645,66660-66665 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r66561 | benjamin.peterson | 2008-09-22 17:13:29 -0500 (Mon, 22 Sep 2008) | 1 line clean up docs for platform's linux_distribution and dist functions ........ r66564 | benjamin.peterson | 2008-09-23 08:32:46 -0500 (Tue, 23 Sep 2008) | 1 line mention how to override boolean evaluation ........ r66580 | georg.brandl | 2008-09-24 04:47:55 -0500 (Wed, 24 Sep 2008) | 2 lines Indentation normalization. ........ r66610 | andrew.kuchling | 2008-09-24 12:27:55 -0500 (Wed, 24 Sep 2008) | 1 line Improve wording ........ r66614 | benjamin.peterson | 2008-09-24 17:11:59 -0500 (Wed, 24 Sep 2008) | 4 lines #3950 fix missing scale factors in turtle.py reviewers: Georg, Benjamin ........ r66618 | benjamin.peterson | 2008-09-25 15:35:45 -0500 (Thu, 25 Sep 2008) | 1 line add a NEWs entry for r66614 ........ r66624 | raymond.hettinger | 2008-09-25 18:31:52 -0500 (Thu, 25 Sep 2008) | 1 line Fix namedtuple bug reported by Glenn Linderman. Template did not form correctly if the field names were input in Unicode. ........ r66625 | benjamin.peterson | 2008-09-25 21:58:36 -0500 (Thu, 25 Sep 2008) | 1 line add the beginnings of a C-API 2 -> 3 porting guide ........ r66628 | benjamin.peterson | 2008-09-26 15:52:06 -0500 (Fri, 26 Sep 2008) | 1 line add an 'other options' section ........ r66629 | georg.brandl | 2008-09-26 16:15:21 -0500 (Fri, 26 Sep 2008) | 2 lines typos. ........ r66643 | andrew.kuchling | 2008-09-27 09:12:33 -0500 (Sat, 27 Sep 2008) | 1 line Add a last bunch of items ........ r66645 | benjamin.peterson | 2008-09-27 11:23:55 -0500 (Sat, 27 Sep 2008) | 1 line 2to3's api should be considered unstable ........ r66660 | andrew.kuchling | 2008-09-27 17:54:08 -0500 (Sat, 27 Sep 2008) | 1 line #3510: future-proof text ........ r66661 | benjamin.peterson | 2008-09-27 18:28:43 -0500 (Sat, 27 Sep 2008) | 1 line clarify a few things ........ r66662 | andrew.kuchling | 2008-09-27 19:15:27 -0500 (Sat, 27 Sep 2008) | 1 line #1579477: mention necessity to flush output before exec'ing ........ r66663 | andrew.kuchling | 2008-09-27 20:08:47 -0500 (Sat, 27 Sep 2008) | 1 line #1415508: Document two functions ........ r66664 | benjamin.peterson | 2008-09-27 20:51:36 -0500 (Sat, 27 Sep 2008) | 1 line better grammar ........ r66665 | benjamin.peterson | 2008-09-27 20:53:29 -0500 (Sat, 27 Sep 2008) | 1 line note the 2to3 -d could be useful for other refactoring ........
2008-09-27 23:06:32 -03:00
Other options
=============
If you are writing a new extension module, you might consider `Cython
<http://cython.org/>`_. It translates a Python-like language to C. The
extension modules it creates are compatible with Python 3 and Python 2.
Devil merge! Merged revisions 66561,66564,66580,66610,66614,66618,66624-66625,66628-66629,66643,66645,66660-66665 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r66561 | benjamin.peterson | 2008-09-22 17:13:29 -0500 (Mon, 22 Sep 2008) | 1 line clean up docs for platform's linux_distribution and dist functions ........ r66564 | benjamin.peterson | 2008-09-23 08:32:46 -0500 (Tue, 23 Sep 2008) | 1 line mention how to override boolean evaluation ........ r66580 | georg.brandl | 2008-09-24 04:47:55 -0500 (Wed, 24 Sep 2008) | 2 lines Indentation normalization. ........ r66610 | andrew.kuchling | 2008-09-24 12:27:55 -0500 (Wed, 24 Sep 2008) | 1 line Improve wording ........ r66614 | benjamin.peterson | 2008-09-24 17:11:59 -0500 (Wed, 24 Sep 2008) | 4 lines #3950 fix missing scale factors in turtle.py reviewers: Georg, Benjamin ........ r66618 | benjamin.peterson | 2008-09-25 15:35:45 -0500 (Thu, 25 Sep 2008) | 1 line add a NEWs entry for r66614 ........ r66624 | raymond.hettinger | 2008-09-25 18:31:52 -0500 (Thu, 25 Sep 2008) | 1 line Fix namedtuple bug reported by Glenn Linderman. Template did not form correctly if the field names were input in Unicode. ........ r66625 | benjamin.peterson | 2008-09-25 21:58:36 -0500 (Thu, 25 Sep 2008) | 1 line add the beginnings of a C-API 2 -> 3 porting guide ........ r66628 | benjamin.peterson | 2008-09-26 15:52:06 -0500 (Fri, 26 Sep 2008) | 1 line add an 'other options' section ........ r66629 | georg.brandl | 2008-09-26 16:15:21 -0500 (Fri, 26 Sep 2008) | 2 lines typos. ........ r66643 | andrew.kuchling | 2008-09-27 09:12:33 -0500 (Sat, 27 Sep 2008) | 1 line Add a last bunch of items ........ r66645 | benjamin.peterson | 2008-09-27 11:23:55 -0500 (Sat, 27 Sep 2008) | 1 line 2to3's api should be considered unstable ........ r66660 | andrew.kuchling | 2008-09-27 17:54:08 -0500 (Sat, 27 Sep 2008) | 1 line #3510: future-proof text ........ r66661 | benjamin.peterson | 2008-09-27 18:28:43 -0500 (Sat, 27 Sep 2008) | 1 line clarify a few things ........ r66662 | andrew.kuchling | 2008-09-27 19:15:27 -0500 (Sat, 27 Sep 2008) | 1 line #1579477: mention necessity to flush output before exec'ing ........ r66663 | andrew.kuchling | 2008-09-27 20:08:47 -0500 (Sat, 27 Sep 2008) | 1 line #1415508: Document two functions ........ r66664 | benjamin.peterson | 2008-09-27 20:51:36 -0500 (Sat, 27 Sep 2008) | 1 line better grammar ........ r66665 | benjamin.peterson | 2008-09-27 20:53:29 -0500 (Sat, 27 Sep 2008) | 1 line note the 2to3 -d could be useful for other refactoring ........
2008-09-27 23:06:32 -03:00