It is formed from a code generator and a Python module.

The code generator processes a set of specification files and generates C or C code which is then compiled to create the bindings extension module. The SIP Python module provides support functions to the automatically generated code.

The specification files contains a description of the interface of the C or C++ library, i.e. the classes, methods, functions and variables.

The format of a specification file is almost identical to a C or C header file, so much so that the easiest way of creating a specification file is to edit the corresponding header file.

SIP makes it easy to exploit existing C or C++ libraries in a productive interpretive programming environment. SIP also makes it easy to take a Python application (maybe a prototype) and selectively implement parts of the application (maybe for performance reasons) in C or C++.