Agfdhyk

Is there a way to specify optional dependencies for a Python package that should be installed by default from pip but for which an install should not be considered a failure if they cannot be installed?

I know that I can specify install_requires so that the packages will be installed for the 90% of users using OSes that can easily install certain optional dependencies, and I also know I can specify extra_require to specify that users can declare they want a full install to get these features, but I haven't found a way to make a default pip install try to install the packages but not complain if they cannot be installed.

(The particular package I'd like to update the setuptools and setup.py for is called music21 for which 95% of the tools can be run without matplotlib, IPython, scipy, pygame, some obscure audio tools etc. but the package gains extra abilities and speed if these packages are installed, and I'd prefer to let people have these abilities by default but not report errors if they cannot be installed)

Not a perfect solution by any means, but you could setup a post-install script to try to install the packages, something like this:

from distutils.core import setup

from distutils import debug





from setuptools.command.install import install

class PostInstallExtrasInstaller(install):

    extras_install_by_default = ['matplotlib', 'nothing']



    @classmethod

    def pip_main(cls, *args, **kwargs):

        def pip_main(*args, **kwargs):

            raise Exception('No pip module found')

        try:

            from pip import main as pip_main

        except ImportError:

            from pip._internal import main as pip_main



        ret = pip_main(*args, **kwargs)

        if ret:

            raise Exception(f'Exitcode {ret}')

        return ret



    def run(self):

        for extra in self.extras_install_by_default:

            try:

                self.pip_main(['install', extra])

            except Exception as E:

                print(f'Optional package {extra} not installed: {E}')

            else:

                print(f"Optional package {extra} installed")

        return install.run(self)





setup(

    name='python-package-ignore-extra-dep-failures',

    version='0.1dev',

    packages=['somewhat',],

    license='Creative Commons Attribution-Noncommercial-Share Alike license',

    install_requires=['requests',],

    extras_require={

        'extras': PostInstallExtrasInstaller.extras_install_by_default,

    },

    cmdclass={

        'install': PostInstallExtrasInstaller,

    },

)

The simplest way to do this is by adding a custom install command that simply shells out to pip to install the "optional" packages. In your setup.py:

import sys

import subprocess

from setuptools import setup

from setuptools.command.install import install



class MyInstall(install):

    def run(self):

        subprocess.call([sys.executable, "-m", "pip", "install", "whatever"])

        install.run(self)



setup(

    ...



    cmdclass={

        'install': MyInstall,

    },

)

Like hoefling said above, this will only work if you publish a source distribution (.tar.gz or .zip). It will not work if you publish your package as a built distribution (.whl).

This might be what you are looking for. It's appears to be a built in feature of setup tools that allows you to declare "optional dependencies".

https://setuptools.readthedocs.io/en/latest/setuptools.html#declaring-extras-optional-features-with-their-own-dependencies

Ex

setup(

    name="Project-A",

    ...

    extras_require={

        'PDF':  ["ReportLab>=1.2", "RXP"],

        'reST': ["docutils>=0.3"],

    }

)