CFFI: calling C from Python

I will introduce CFFI, a way to call C libraries from Python.

http://cffi.readthedocs.org/

CFFI was designed in 2012 to get away from Python’s C extension modules, which require hand-written CPython-specific C code. CFFI is arguably simpler to use: you call C from Python directly, instead of going through an intermediate layer. It is not tied to CPython’s internals, and works natively on two different Python implementations: CPython and PyPy. It could be ported to more implementations.

It is also a big success, according to the download statistics. Some high-visibility projects like Cryptography have switched to it.

Part of the motivation for developing CFFI is that it is a minimal layer that allows direct access to C from Python, with no fixed intermediate C API. It shares ideas from Cython, ctypes, and LuaJIT’s ffi, but the non-dependence on any fixed C API is a central point.

It is a possible solution to a problem that hits notably PyPy — the CPython C API. The CPython C API was great and, we can argue, it contributed a lot to the present-day success of Python, together with tools built on top of it like Cython and SWIG. However, it may be time to look beyond it. This talk will thus present CFFI as such an example. This independence is what lets CFFI work equally well on CPython and on PyPy (and be very fast on the latter thanks to the JIT compiler).