21.1 Defining a library

First consider LibUtilities. An abbreviated version of the base file, LibUtilities.cpp has the following structure:

1#include <LibUtilities/Python/NekPyConfig.hpp> 
2 
3void export_Basis(); 
4void export_SessionReader(); 
5 
6BOOST_PYTHON_MODULE(_LibUtilities) 
7{ 
8    // Initialise Boost.NumPy. 
9    np::initialize(); 
10 
11    // Export classes. 
12    export_Basis(); 
13    export_SessionReader(); 
14}

The BOOST_PYTHON_MODULE(name) macro allows us to define a Python module inside C++. Note that in this case, the leading underscore in the name (i.e. _LibUtilities) is deliberate. To define the contents of the module, we call a number of functions that are prefixed by export_, which will define one or more Python classes that live in this module. These Python classes correspond with our Nektar++ classes. We adopt this approach simply so that we can split up the different classes into different files, because it is not possible to call BOOST_PYTHON_MODULE more than once. These functions are defined in appropriately named files, for example export_Basis() lives in the file LibUtilities/Python/Foundations/Basis.cpp. This corresponds to the Nektar++ file LibUtilities/Foundations/Basis.cpp and the classes defined therein.