#### Overview of this book

Cython is a hybrid programming language used to write C extensions for Python language. Combining the practicality of Python and speed and ease of the C language it’s an exciting language worth learning if you want to build fast applications with ease. This new edition of Learning Cython Programming shows you how to get started, taking you through the fundamentals so you can begin to experience its unique powers. You’ll find out how to get set up, before exploring the relationship between Python and Cython. You’ll also look at debugging Cython, before moving on to C++ constructs, Caveat on C++ usage, Python threading and GIL in Cython. Finally, you’ll learn object initialization and compile time, and gain a deeper insight into Python 3, which will help you not only become a confident Cython developer, but a much more fluent Python developer too.
Learning Cython Programming Second Edition
Credits
Acknowledgments
www.PacktPub.com
Preface
Free Chapter
Cython Won't Bite
Understanding Cython
Extending Applications
Debugging Cython
Index

## Cython pure Python code

Let's view a mathematical application that is actually taken from the Cython documentation. I wrote this equivalent in pure Python so that we can compare the speed. If you open the `primes` example for this chapter, you will see two programs—the Cython `primes.pyx` example, and my pure Python port. They both look almost the same:

```def primes(kmax):
n = 0
k = 0
i = 0
if kmax > 1000:
kmax = 1000
p = [0] * kmax
result = []
k = 0
n = 2
while k < kmax:
i = 0
while i < k and n % p[i] != 0:
i = i + 1
if i == k:
p[k] = n
k = k + 1
result.append(n)
n = n + 1
return result
primes (10000)```

This really is a direct Python port of that Cython code. Both call `primes (10000)`, but the evaluation time is very different between them in terms of performance:

```\$ make
cython --embed primes.pyx
gcc -g -O2 -c primes.c -o primes.o `python-config --includes`
gcc ...```