I've been seeing some examples of Python being used with c++, and I'm trying to understand why would someone want to do it. What are the benefits of calling C++ code from an external language such as Python?
I'd appreciate a simple example - Boost::Python will do
Here's two possibilities:

Perhaps the C++ code is already written & available for use. 
It's likely the C++ code is faster/smaller than equivalent Python
Practical point of view: Why would I want to use Python with C++?