simple-cython-example

Basic example of how to wrap a C function with cython.

To install this python module, use:

git clone https://github.com/PiRK/simple-cython-example.git
cd simple-cython-example
pip install . --user

Then, in a python interactive shell:

>>> import mymax
>>> dir(mymax)
['__builtins__', '__doc__', '__file__', '__name__', '__package__', '__test__', 'pyhello', 'pymax']
>>> mymax.pymax(12, 15.1)
print from python function wrapping a c function
print from c function
>>> mymax.pyhello()
Hello World
3.141593 2.718282
print from c function
max of e and pi is approximately 3.141593

This example includes 2 .c files, 1 .h file, 1 .pyx file, 1 .pxd file and a setup.py file.

The .pyx contains the cython function definition.

The .pxd file wraps the .c functions (through their declaration in the .h file).

The setup.py file is a standard way of building and installing python libraries (read https://docs.python.org/3/distutils/setupscript.html or http://python-packaging.readthedocs.io/en/latest/minimal.html for more information on this). The less standard part of this file is the from Cython.Distutils import build_ext import. This replaces the standard setuptools or distutils build_ext command with a version that can handle conversion of cython code into standard C code that uses the Python.h library and that can be compiled by setuptools.

This example is simple because the C-function don't take as argument (and don't return) pointers/arrays. If you want to achieve this, you should look at more complicated examples using numpy arrays and memory views, such as https://github.com/silx-kit/silx/blob/master/silx/math/fit/functions.pyx .