Definitions in py3c

This table summarizes the various macros py3c defines, or mentions in the Porting Guide.

Macro py2 py3
IS_PY3 → 0 → 1
PyStr_* → PyString_* → PyUnicode_*
PyBytes_* → PyString_* ✔
PyUnicode_* ✔ ✔
PyString_* ✔ error
PyStr_AsUTF8AndSize see below ✔
PyInt_* ✔ → PyLong_*
PyLong_* ✔ ✔
PyFloat_FromString see below ✔
PyModuleDef see below ✔
PyModuleDef_HEAD_INIT → 0 ✔
PyModule_Create see below ✔
MODULE_INIT_FUNC see below see below
Rich comparisons ✔ ✔
Py_RETURN_RICHCOMPARE = =
Py_RETURN_NOTIMPLEMENTED = =
Py_UNREACHABLE = =
PY3C_RICHCMP see below see below
Py_TYPE ✔ ✔
Py_REFCNT ✔ ✔
Py_SIZE ✔ ✔
PyVarObject_HEAD_INIT ✔ ✔
PyCapsule_* see below ✔
Py_TPFLAGS_* ✔ see below
PyMem_Raw* = =
Py_UNUSED = =

Legend:

✔ – provided by Python
→ – defined in py3c as a simple alias for
= – provided by at least Python 3.7; py3c backports it to Python versions that don’t define it

The following non-trivial macros are defined:

PyStr_AsUTF8AndSize()

Python 2: defined in terms of PyString_Size and PyString_AsString. Differences from Python 3:

  • no encoding (string is assumed to be UTF-8-encoded)
  • size pointer must not be NULL
  • size may be stored even if an error occurs
PyFloat_FromSting()
Python 2: Only takes one argument, as in Python 3.
PyModuleDef
Python 2: contains m_name, m_doc, m_size, m_methods fields from Python 3, and m_base to accomodate PyModuleDef_HEAD_INIT.
PyModule_Create()
Python 2: calls Py_InitModule3; semantics same as in Python 3
MODULE_INIT_FUNC(<mod>)
Python 3: declares PyInit_<mod> and provides function header for it
Python 2: declares & defines init<mod>; declares a static PyInit_<mod> and provides function header for it
PY3C_RICHCMP()
Convenience macro for comparisons, same in both versions.
Deprecated; use Py_RETURN_RICHCOMPARE instead.
PyCapsule_*
Capsules are included in Python 2.7 and 3.1+.
For 2.6, see the chapter PyCapsule API for Python 2.6.
Py_TPFLAGS_*
Type flags that were removed in Python 3 are defined to 0 in <py3c/tpflags.h>. Read the documentation before including the file.