.. highlightlang:: c
.. sectionauthor:: Martin v. Löwis <martin@v.loewis.de>
Starting in Python 1.4, Python provides, on Unix, a special make file for building make files for building dynamically-linked extensions and custom interpreters. Starting with Python 2.0, this mechanism (known as related to Makefile.pre.in, and Setup files) is no longer supported. Building custom interpreters was rarely used, and extension modules can be built using distutils.
Building an extension module using distutils requires that distutils is installed on the build machine, which is included in Python 2.x and available separately for Python 1.5. Since distutils also supports creation of binary packages, users don't necessarily need a compiler and distutils to install the extension.
A distutils package contains a driver script, :file:`setup.py`. This is a plain Python file, which, in the most simple case, could look like this:
from distutils.core import setup, Extension
module1 = Extension('demo',
sources = ['demo.c'])
setup (name = 'PackageName',
version = '1.0',
description = 'This is a demo package',
ext_modules = [module1])
With this :file:`setup.py`, and a file :file:`demo.c`, running
python setup.py build
will compile :file:`demo.c`, and produce an extension module named demo in
the :file:`build` directory. Depending on the system, the module file will end
up in a subdirectory :file:`build/lib.system`, and may have a name like
:file:`demo.so` or :file:`demo.pyd`.
In the :file:`setup.py`, all execution is performed by calling the setup
function. This takes a variable number of keyword arguments, of which the
example above uses only a subset. Specifically, the example specifies
meta-information to build packages, and it specifies the contents of the
package. Normally, a package will contain of addition modules, like Python
source modules, documentation, subpackages, etc. Please refer to the distutils
documentation in :ref:`distutils-index` to learn more about the features of
distutils; this section explains building extension modules only.
It is common to pre-compute arguments to :func:`setup`, to better structure the
driver script. In the example above, theext_modules argument to
:func:`setup` is a list of extension modules, each of which is an instance of
the :class:`~distutils.extension.Extension`. In the example, the instance
defines an extension named demo which is build by compiling a single source
file, :file:`demo.c`.
In many cases, building an extension is more complex, since additional preprocessor defines and libraries may be needed. This is demonstrated in the example below.
from distutils.core import setup, Extension
module1 = Extension('demo',
define_macros = [('MAJOR_VERSION', '1'),
('MINOR_VERSION', '0')],
include_dirs = ['/usr/local/include'],
libraries = ['tcl83'],
library_dirs = ['/usr/local/lib'],
sources = ['demo.c'])
setup (name = 'PackageName',
version = '1.0',
description = 'This is a demo package',
author = 'Martin v. Loewis',
author_email = 'martin@v.loewis.de',
url = 'http://docs.python.org/extending/building',
long_description = '''
This is really just a demo package.
''',
ext_modules = [module1])
In this example, :func:`setup` is called with additional meta-information, which is recommended when distribution packages have to be built. For the extension itself, it specifies preprocessor defines, include directories, library directories, and libraries. Depending on the compiler, distutils passes this information in different ways to the compiler. For example, on Unix, this may result in the compilation commands
gcc -DNDEBUG -g -O3 -Wall -Wstrict-prototypes -fPIC -DMAJOR_VERSION=1 -DMINOR_VERSION=0 -I/usr/local/include -I/usr/local/include/python2.2 -c demo.c -o build/temp.linux-i686-2.2/demo.o gcc -shared build/temp.linux-i686-2.2/demo.o -L/usr/local/lib -ltcl83 -o build/lib.linux-i686-2.2/demo.so
These lines are for demonstration purposes only; distutils users should trust that distutils gets the invocations right.
When an extension has been successfully build, there are three ways to use it.
End-users will typically want to install the module, they do so by running
python setup.py install
Module maintainers should produce source packages; to do so, they run
python setup.py sdist
In some cases, additional files need to be included in a source distribution; this is done through a :file:`MANIFEST.in` file; see the distutils documentation for details.
If the source distribution has been build successfully, maintainers can also create binary distributions. Depending on the platform, one of the following commands can be used to do so.
python setup.py bdist_wininst python setup.py bdist_rpm python setup.py bdist_dumb