Execute a Python script post install using distutils / setuptools

Question

I'm trying to add a post-install task to Python distutils as described in How to extend distutils with a simple post install script?. The task is supposed to execute a Python script in the installed lib directory. This script generates additional Python modules the installed package requires.

My first attempt is as follows:

from distutils.core import setup
from distutils.command.install import install

class post_install(install):
    def run(self):
        install.run(self)
        from subprocess import call
        call(['python', 'scriptname.py'],
             cwd=self.install_lib + 'packagename')

setup(
 ...
 cmdclass={'install': post_install},
)

This approach works, but as far as I can tell has two deficiencies:

1. If the user has used a Python interpreter other than the one picked up from PATH, the post install script will be executed with a different interpreter which might cause a problem.
2. It's not safe against dry-run etc. which I might be able to remedy by wrapping it in a function and calling it with distutils.cmd.Command.execute.

How could I improve my solution? Is there a recommended way / best practice for doing this? I'd like to avoid pulling in another dependency if possible.

Answer 1

The way to address these deficiences is:

1. Get the full path to the Python interpreter executing setup.py from sys.executable.

2. Classes inheriting from distutils.cmd.Command (such as distutils.command.install.install which we use here) implement the execute method, which executes a given function in a "safe way" i.e. respecting the dry-run flag.

   Note however that the --dry-run option is currently broken and does not work as intended anyway.

I ended up with the following solution:

import os, sys
from distutils.core import setup
from distutils.command.install import install as _install


def _post_install(dir):
    from subprocess import call
    call([sys.executable, 'scriptname.py'],
         cwd=os.path.join(dir, 'packagename'))


class install(_install):
    def run(self):
        _install.run(self)
        self.execute(_post_install, (self.install_lib,),
                     msg="Running post install task")


setup(
    ...
    cmdclass={'install': install},
)

Note that I use the class name install for my derived class because that is what python setup.py --help-commands will use.

Answer 2

I think the easiest way to perform the post-install, and keep the requirements, is to decorate the call to setup(...):

from setup tools import setup


def _post_install(setup):
    def _post_actions():
        do_things()
    _post_actions()
    return setup

setup = _post_install(
    setup(
        name='NAME',
        install_requires=['...
    )
)

This will run setup() when declaring setup. Once done with the requirements installation, it will run the _post_install() function, which will run the inner function _post_actions().