Migrating C extensions — Supporting Python 3: An in-depth guideMigrating C extensions¶ Python 3 has many changes to the C API, including in the API for defining classes and initializing modules. This means that every single C extension has to be modified to run under Python 3. Some of the changes are simple and some are not, but you will have to do them all by hand as 2to3 only handles Python code. That also means that you can’t support Python 2 and Python 3
Python/C API Reference Manual — Python v3.2.2 documentation
