How to extend distutils with a simple post install script?

I dug through distutils source for a day to learn enough about it to make a bunch of custom commands. It's not pretty, but it does work.

import distutils.core
from distutils.command.install import install
...
class my_install(install):
    def run(self):
        install.run(self)
        # Custom stuff here
        # distutils.command.install actually has some nice helper methods
        # and interfaces. I strongly suggest reading the docstrings.
...
distutils.core.setup(..., cmdclass=dict(install=my_install), ...)

OK, I figured it out. The idea is basically to extend one of the distutils commands and overwrite the run method. To tell distutils to use the new class you can use the cmdclass variable.

from distutils.core import setup
from distutils.command.install_data import install_data

class post_install(install_data):
    def run(self):
        # Call parent 
        install_data.run(self)
        # Execute commands
        print "Running"

setup(name="example",
      cmdclass={"install_data": post_install},
      ...
      )

Hope this will help someone else.

I couldn't make Joe Wreschnigs answer work and tweaked his answer analogous to the extending distutils documentation. I came up with this code which works fine on my machine.

from distutils import core
from distutils.command.install import install
...
class my_install(install):
    def run(self):
        install.run(self)
        # Custom stuff here
        # distutils.command.install actually has some nice helper methods
        # and interfaces. I strongly suggest reading the docstrings.
...
distutils.core.setup(..., cmdclass={'install': my_install})

Note: I didn't edit the answer of Joe since I am uncertain why his answer wasn't working on my machine.

I got an error when I tried the accepted answer here (might be because I'm using Python 2.6 in this particular case, not sure). This occurred for both 'setup.py install' and 'pip install':

sudo python setup.py install

fails with error: error in setup.cfg: command 'my_install' has no such option 'single_version_externally_managed'

AND

sudo pip install . -U

fails more verbosely but also with error: option --single-version-externally-managed not recognized

Variation on the accepted answer

Replacing the imports from distutils with setuptools solved the problem for me:

from setuptools import setup
from setuptools.command.install import install