The last example is about approximating factorials with Cython. We will use two approximation methods. First, we will use the Stirling approximation method (see http://en.wikipedia.org/wiki/Stirling%27s_approximation for more information). The formula for the Stirling approximation is:
Secondly, we will be using the approximation due to Ramanujan, with the following formula:
This section describes how to approximate factorials using Cython. In this recipe, we will be using types, which as you may remember, is optional in Cython. In theory, declaring static types should speed things up. Static typing offers interesting challenges that you may not encounter when writing Python code, but don't worry, we will try to keep it simple.