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..
Copyright (c) 2015, Red Hat, Inc. and/or its affiliates
Licensed under CC-BY-SA-3.0; see the license file
.. highlight:: c
.. index::
single: Cleanup
Cleanup – Dropping Support for Python 2
=======================================
When users of your C extension are not using Python 2 any more, or you need to
use one of Python 3's irresistible new features, you can convert the project to
use Python 3 only.
As mentioned earlier, it is usually not a good idea to do this until you
have full support for both Pythons.
With py3c, dropping Python 2 basically amounts to expanding all its compat
macros.
In other words, remove the ``py3c.h`` header, and fix the compile errors.
* .. index::
double: Cleanup; Strings
double: Cleanup; Bytes
double: Cleanup; Unicode
Convert ``PyStr_*`` to ``PyUnicode_*``; ``PyInt_*`` to ``PyLong_*``.
* .. index::
double: Cleanup; Module Initialization
Instead of ``MODULE_INIT_FUNC(<name>)``, write::
PyMODINIT_FUNC PyInit_<name>(void);
PyMODINIT_FUNC PyInit_<name>(void)
* .. index::
double: Cleanup; Types
Remove ``Py_TPFLAGS_HAVE_WEAKREFS`` and ``Py_TPFLAGS_HAVE_ITER``
(py3c defines them as 0).
* .. index::
double: Cleanup; Comparisons
Replace ``return PY3C_RICHCMP`` by :c:func:`Py_RETURN_RICHCOMPARE`,
as mentioned in :c:macro:`PY3C_RICHCMP` documentation.
* Replace :c:func:`Py_RETURN_RICHCOMPARE` and :c:func:`Py_UNREACHABLE`
by its expansion, unless you either
support Python 3.7+ only or keep the ``py3c/comparison.h`` header.
* Replace :c:func:`Py_RETURN_NOTIMPLEMENTED` by its expansion, unless you either
support Python 3.3+ only or keep the ``py3c/comparison.h`` header.
* Drop ``capsulethunk.h``, if you're using it.
* Remove any code in ``#if !IS_PY3`` blocks, and the ifs around
``#if IS_PY3`` ones.
You will want to check the code as you're doing this.
For example, replacing PyLong can easily result in code like
``if (PyInt_Check(o) || PyInt_Check(o))``.
Enjoy your Python 3-compatible extension!
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