Installation and Status¶
Quick installation for CPython (cffi is distributed with PyPy):
pip install cffi
- or get the source code via the Python Package Index.
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.
- 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.verify(); or installing such 3rd-party modules from sources.
- on CPython, on non-Windows platforms, you also need to install
libffi-devin order to compile CFFI itself.
- pycparser >= 2.06: https://github.com/eliben/pycparser (automatically
pip install cffi).
- py.test is needed to run the tests of CFFI itself.
Download and Installation:
Checksums of the “source” package version 1.11.4:
- MD5: 8ef0f852498908b20bc508799901fe93
- SHA: d0c4f7d4b6af4c438a17b2f2334f2aa5ff7cc4db
- SHA256: df9083a992b17a28cd4251a3f5c879e0198bb26c9e808c4647e0a18739f1d11d
Or grab the most current version from the Bitbucket page:
hg clone https://bitbucket.org/cffi/cffi
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)
- The demo directory contains a number of small and large demos
- The documentation below might be sketchy on details; for now the ultimate reference is given by the tests, notably testing/cffi1/test_verify1.py and testing/cffi0/backend_tests.py.
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.
Homebrew (Thanks David Griffin for this)
- Install homebrew: http://brew.sh
- Run the following commands in a terminal
brew install pkg-config libffi PKG_CONFIG_PATH=/usr/local/opt/libffi/lib/pkgconfig pip install cffi
Alternatively, 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 = 
include_dirs = ['/usr/local/lib/libffi-3.0.11/include']
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:
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
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
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
If you are using
pyenv, then see
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:
~/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.
You need to make sure you have an up-to-date version of libffi, which fixes some bugs.