distutils: How to pass a user defined parameter to setup.py?

As Setuptools/Distuils are horribly documented, I had problems finding the answer to this myself. But eventually I stumbled across this example. Also, this similar question was helpful. Basically, a custom command with an option would look like:

from distutils.core import setup, Command

class InstallCommand(Command):
    description = "Installs the foo."
    user_options = [
        ('foo=', None, 'Specify the foo to bar.'),
    ]
    def initialize_options(self):
        self.foo = None
    def finalize_options(self):
        assert self.foo in (None, 'myFoo', 'myFoo2'), 'Invalid foo!'
    def run(self):
        install_all_the_things()

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

Here is a very simple solution, all you have to do is filter out sys.argv and handle it yourself before you call to distutils setup(..). Something like this:

if "--foo" in sys.argv:
    do_foo_stuff()
    sys.argv.remove("--foo")
...
setup(..)

The documentation on how to do this with distutils is terrible, eventually I came across this one: the hitchhikers guide to packaging, which uses sdist and its user_options. I find the extending distutils reference not particularly helpful.

Although this looks like the "proper" way of doing it with distutils (at least the only one that I could find that is vaguely documented). I could not find anything on --with and --without switches mentioned in the other answer.

The problem with this distutils solution is that it is just way too involved for what I am looking for (which may also be the case for you). Adding dozens of lines and subclassing sdist is just wrong for me.

You can't really pass custom parameters to the script. However the following things are possible and could solve your problem:

• optional features can be enabled using --with-featurename, standard features can be disabled using --without-featurename. [AFAIR this requires setuptools]
• you can use environment variables, these however require to be set on windows whereas prefixing them works on linux/ OS X (FOO=bar python setup.py).
• you can extend distutils with your own cmd_classes which can implement new features. They are also chainable, so you can use that to change variables in your script. (python setup.py foo install) will execute the foo command before it executes install.

Hope that helps somehow. Generally speaking I would suggest providing a bit more information what exactly your extra parameter should do, maybe there is a better solution available.

To be fully compatible with both python setup.py install and pip install . you need to use environment variables because pip option --install-option= is bugged:

1. pip --install-option leaks across lines
2. Determine what should be done about --(install|global)-option with Wheels
3. pip not naming abi3 wheels correctly

This is a full example not using the --install-option:

import os
environment_variable_name = 'MY_ENVIRONMENT_VARIABLE'
environment_variable_value = os.environ.get( environment_variable_name, None )

if environment_variable_value is not None:
    sys.stderr.write( "Using '%s=%s' environment variable!\n" % (
            environment_variable_name, environment_variable_value ) )

setup(
        name = 'packagename',
        version = '1.0.0',
        ...
)

Then, you can run it like this on Linux:

MY_ENVIRONMENT_VARIABLE=1 pip install .
MY_ENVIRONMENT_VARIABLE=1 pip install -e .
MY_ENVIRONMENT_VARIABLE=1 python setup.py install
MY_ENVIRONMENT_VARIABLE=1 python setup.py develop

But, if you are on Windows, run it like this:

set "MY_ENVIRONMENT_VARIABLE=1" && pip install .
set "MY_ENVIRONMENT_VARIABLE=1" && pip install -e .
set "MY_ENVIRONMENT_VARIABLE=1" && python setup.py install
set "MY_ENVIRONMENT_VARIABLE=1" && python setup.py develop

References:

1. How to obtain arguments passed to setup.py from pip with '--install-option'?
2. Passing command line arguments to pip install
3. Passing the library path as a command line argument to setup.py