Cython to Wrap Existing C Code

What is Cython ? 

It is an optimizing static compiler for both the Python programming language and the extended Cython programming language. It is used to make it easy to write C extensions for Python as easy as Python itself.

It comes up with many helpful features :

• Writing a Python code that calls back and forth from and to C/C++ code.
• Easily tuning of readable Python code into plain C performance by adding static type declarations.
• Use of combined source code level debugging to find bugs in given Python, Cython and C code.
• Efficient interaction with large data sets, e.g. using multi-dimensional NumPy arrays.
• Integration with existing code and data from low-level or high-performance libraries and applications.

To make an extension with Cython is a tricky task to perform. Doing so, one needs to create a collection of wrapper functions. Assuming that the work code shown has been compiled into a C library called libwork. The code below will create a file named csample.pxd.

Code #1 :

# cwork.pxd 

# 

# Declarations of "external" C 

# functions and structures 

cdef extern from "work.h": 

int gcd(int, int) 

int divide(int, int, int *) 

double avg(double *, int) nogil 

ctypedef struct Point: 

double x 

double y 

double distance(Point *, Point *) 

In Cython, the code above will work as a C header file. The initial declaration cdef externfrom "work.h" declares the required C header file. Declarations that follow are taken from the header. The name of this file is cwork.pxd. Next target is to create a work.pyx file which will define wrappers that bridge the Python interpreter to the underlying C code declared in the cwork.pxd file.