Building Cython code¶
Cython code must, unlike Python, be compiled. This happens in two stages:
- A
.pyx
file is compiled by Cython to a.c
file, containing the code of a Python extension module- The
.c
file is compiled by a C compiler to a.so
file (or.pyd
on Windows) which can beimport
-ed directly into a Python session.
There are several ways to build Cython code:
- Write a distutils
setup.py
.- Use
pyximport
, importing Cython.pyx
files as if they were.py
files (using distutils to compile and build the background).- Run the
cython
command-line utility manually to produce the.c
file from the.pyx
file, then manually compiling the.c
file into a shared object library or.dll
suitable for import from Python. (This is mostly for debugging and experimentation.)- Use the [Sage] notebook which allows Cython code inline.
Currently, distutils is the most common way Cython files are built and distributed. The other methods are described in more detail in the Source Files and Compilation section of the reference manual.
Building a Cython module using distutils¶
Imagine a simple “hello world” script in a file hello.pyx
:
def say_hello_to(name):
print("Hello %s!" % name)
The following could be a corresponding setup.py
script:
from distutils.core import setup
from distutils.extension import Extension
from Cython.Distutils import build_ext
ext_modules = [Extension("hello", ["hello.pyx"])]
setup(
name = 'Hello world app',
cmdclass = {'build_ext': build_ext},
ext_modules = ext_modules
)
To build, run python setup.py build_ext --inplace
. Then simply
start a Python session and do from hello import say_hello_to
and
use the imported function as you see fit.
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