============
Build System
============

If you want to use Python with other programming languages, a build system is
usually needed.  A build system is used to `automate the processes of
compiling, linking, packaging, and deploying software
<http://en.wikipedia.org/wiki/Build_automation>`__.  This chapter will focus on
a tool called `SCons <http://www.scons.org/>`_, which is implement with pure
Python.  Building scripts of SCons can be highly modularized and reused, and
cross-platform as well.

Using a build system involves writing building scripts.  Building scripts of
SCons can have three parts:

- Front-end script (``SConstruct``),
- Rule script (``Sconscript``), and
- Tools (``site_scons/site_tools/*``).

Below is the ``SConstruct`` and the ``SConscript`` files of an example project.
The ``SConstruct`` file is:

.. literalinclude:: ../../examples/inter_build/SConstruct
  :language: python

The ``SConscript`` file is:

.. literalinclude:: ../../examples/inter_build/SConscript
  :language: python

SCons tools provide a means to reuse the building code.  For example, we can
use the `SCons tools provided by the Cython team
<https://github.com/cython/cython/tree/master/Tools/site_scons/site_tools>`__
to build your cython code, by copying the files ``cython.py`` and ``pyext.py``
into the directory ``site_scons/site_tools`` inside your project.

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