Installation and Status

Quick installation for CPython (cffi is distributed with PyPy):

In more details:

This code has been developed on Linux, but should work on any POSIX platform as well as on Windows 32 and 64. (It relies occasionally on libffi, so it depends on libffi being bug-free; this may not be fully the case on some of the more exotic platforms.)

CFFI supports CPython 2.6, 2.7, 3.x (tested with 3.2 to 3.4); and is distributed with PyPy (CFFI 1.0 is distributed with and requires PyPy 2.6).

The core speed of CFFI is better than ctypes, with import times being either lower if you use the post-1.0 features, or much higher if you don’t. The wrapper Python code you typically need to write around the raw CFFI interface slows things down on CPython, but not unreasonably so. On PyPy, this wrapper code has a minimal impact thanks to the JIT compiler. This makes CFFI the recommended way to interface with C libraries on PyPy.

Requirements:

  • CPython 2.6 or 2.7 or 3.x, or PyPy (PyPy 2.0 for the earliest versions of CFFI; or PyPy 2.6 for CFFI 1.0).
  • in some cases you need to be able to compile C extension modules; refer to the appropriate docs for your OS. This includes installing CFFI from sources; or developing code based on ffi.set_source() or ffi.verify(); or installing such 3rd-party modules from sources.
  • on CPython, on non-Windows platforms, you also need to install libffi-dev in order to compile CFFI itself.
  • pycparser >= 2.06: https://github.com/eliben/pycparser (automatically tracked by pip install cffi).
  • py.test is needed to run the tests of CFFI itself.

Download and Installation:

  • http://pypi.python.org/packages/source/c/cffi/cffi-1.10.0.tar.gz

    • MD5: 2b5fa41182ed0edaf929a789e602a070
    • SHA: 8484aba03d1e64367d3110c0e36c1ed052b43f12
    • SHA256: b3b02911eb1f6ada203b0763ba924234629b51586f72a21faacc638269f4ced5
  • Or grab the most current version from the Bitbucket page: hg clone https://bitbucket.org/cffi/cffi

  • python setup.py install or python setup_base.py install (should work out of the box on Linux or Windows; see below for MacOS X or Windows 64.)

  • running the tests: py.test  c/  testing/ (if you didn’t install cffi yet, you need first python setup_base.py build_ext -f -i)

Demos:

Platform-specific instructions

libffi is notoriously messy to install and use — to the point that CPython includes its own copy to avoid relying on external packages. CFFI does the same for Windows, but not for other platforms (which should have their own working libffi’s). Modern Linuxes work out of the box thanks to pkg-config. Here are some (user-supplied) instructions for other platforms.

MacOS X

Homebrew (Thanks David Griffin for this)

  1. Install homebrew: http://brew.sh
  2. Run the following commands in a terminal
brew install pkg-config libffi
PKG_CONFIG_PATH=/usr/local/opt/libffi/lib/pkgconfig pip install cffi

Aternatively, on OS/X 10.6 (Thanks Juraj Sukop for this)

For building libffi you can use the default install path, but then, in setup.py you need to change:

include_dirs = []

to:

include_dirs = ['/usr/local/lib/libffi-3.0.11/include']

Then running python setup.py build complains about “fatal error: error writing to -: Broken pipe”, which can be fixed by running:

ARCHFLAGS="-arch i386 -arch x86_64" python setup.py build

as described here.

Windows (regular 32-bit)

Win32 works and is tested at least each official release.

The recommended C compiler compatible with Python 2.7 is this one: http://www.microsoft.com/en-us/download/details.aspx?id=44266 There is a known problem with distutils on Python 2.7, as explained in https://bugs.python.org/issue23246, and the same problem applies whenever you want to run compile() to build a dll with this specific compiler suite download. import setuptools might help, but YMMV

For Python 3.4 and beyond: https://www.visualstudio.com/en-us/downloads/visual-studio-2015-ctp-vs

Windows 64

Win64 received very basic testing and we applied a few essential fixes in cffi 0.7. The comment above applies for Python 2.7 on Windows 64 as well. Please report any other issue.

Note as usual that this is only about running the 64-bit version of Python on the 64-bit OS. If you’re running the 32-bit version (the common case apparently), then you’re running Win32 as far as we’re concerned.

Linux and OS/X: UCS2 versus UCS4

This is about getting an ImportError about _cffi_backend.so with a message like Symbol not found: _PyUnicodeUCS2_AsASCIIString. This error occurs in Python 2 as soon as you mix “ucs2” and “ucs4” builds of Python. It means that you are now running a Python compiled with “ucs4”, but the extension module _cffi_backend.so was compiled by a different Python: one that was running “ucs2”. (If the opposite problem occurs, you get an error about _PyUnicodeUCS4_AsASCIIString instead.)

If you are using pyenv, then see https://github.com/yyuu/pyenv/issues/257.

More generally, the solution that should always work is to download the sources of CFFI (instead of a prebuilt binary) and make sure that you build it with the same version of Python than the one that will use it. For example, with virtualenv:

  • virtualenv ~/venv
  • cd ~/path/to/sources/of/cffi
  • ~/venv/bin/python setup.py build --force # forcing a rebuild to make sure
  • ~/venv/bin/python setup.py install

This will compile and install CFFI in this virtualenv, using the Python from this virtualenv.