Suppose we have the following C++ API which we want to expose in Python: 
{{{
#include <string>

namespace { // Avoid cluttering the global namespace.

  // A couple of simple C++ functions that we want to expose to Python.
  std::string greet() { return "hello, world"; }
  int square(int number) { return number * number; }
}
}}}
Here is the C++ code for a python module called getting_started1 which exposes the API. 
{{{
#include <boost/python.hpp>
using namespace boost::python;

BOOST_PYTHON_MODULE(getting_started1)
{
    // Add regular functions to the module.
    def("greet", greet);
    def("square", square);
}
}}}
That's it! If we build this shared library and put it on our PYTHONPATH we can now access our C++ functions from Python. 
{{{
>>> import getting_started1
>>> print getting_started1.greet()
hello, world
>>> number = 11
>>> print number, '*', number, '=', getting_started1.square(number)
11 * 11 = 121
}}}