How should I handle importing third-party libraries within my setup.py script?

问题

I'm developing a Python application and in the process of branching off a release. I've got a PyPI server set up on a company server and I've copied a source distribution of my package onto it.

I checked that the package was being hosted on the server and then tried installing it on my local development machine. I ended up with this output:

$ pip3 install --trusted-host 172.16.1.92 -i http://172.16.1.92:5001/simple/ <my-package>
Collecting <my-package>
  Downloading http://172.16.1.92:5001/packages/<my-package>-0.2.0.zip
    Complete output from command python setup.py egg_info:
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "C:\Users\<me>\AppData\Local\Temp\pip-build-ubb3jkpr\<my-package>\setup.py", line 9, in <module>
        import appdirs
    ModuleNotFoundError: No module named 'appdirs'

    ----------------------------------------
Command "python setup.py egg_info" failed with error code 1 in C:\Users\<me>\AppData\Local\Temp\pip-build-ubb3jkpr\<my-package>\

The reason is that I'm trying to import a third-party library appdirs in my setup.py, which is necessary for me to compute the data_files argument to setup():

try:
    from setuptools import setup
except ImportError:
    from distutils.core import setup

import os
from collections import defaultdict

import appdirs
from <my-package>.version import __version__ as <my-package>_version

APP_NAME = '<my-app>'
APP_AUTHOR = '<company>'
SYSTEM_COMPONENT_PLUGIN_DIR = os.path.join(appdirs.user_data_dir(APP_NAME, APP_AUTHOR), 'components')

# ...

setup(
    # ...
    data_files=component_files,
)

However, I don't have appdirs installed on my local dev machine and I don't expect the end users to have it either.

Is it acceptable to rely on third-party libraries like this in setup.py, and if so what is the recommended approach to using them? Is there a way I can ensure appdirs gets installed before it's imported in setup.py, or should I just document that appdirs is a required package to install my package?

回答1:

I'm ignoring licensing issues in this answer. You definetly need to take these into account before you really do a release.

Is it acceptable to rely on third-party libraries like this in setup.py

Yes, it is acceptable but generally these should be minimized, especially if these are modules which have no obvious use for the end-user. Noone likes to have packages they don't need or use.

what is the recommended approach to using them?

There are basically 3 options:

Bootstrap them (for example use pip to programmatically install packages). For example setuptools provides an ez_setup.py file that can be used to bootstrap setuptools. Maybe that can be customized to download and install appdirs.
Include them (especially if it's a small package) in your project. For example appdirs is basically just a single file module. Pretty easy to copy and maintain in your project. Be very careful with licensing issues when you do that!

Fail gracefully when it's not possible to import them and let the user install them. For example:

try:
    import appdirs
except ImportError:
    raise ImportError('this package requires "appdirs" to be installed. '
                      'Install it first: "pip install appdirs".')

回答2:

You can mention install_requires with the dependencies list. Please check the python packaging guide here. Also you can provide a requirements.txt file so that it can be run at once using "pip install -r"

回答3:

You could use pip to install the package programmatically if the import fails:

try:
    import appdirs
except ImportError:
    import pip
    pip.main(['install', 'appdirs'])
    import appdirs

In some circumstances you may need to use importlib or __import__ to import the package after pip.main or referesh the PATH variable. It could also be worthwhile to include a verification if the user really wants to install that package before installing it.

I used a lot of the examples from "Installing python module within code" and I haven't personally tried used this in setup.py files but it looks like it could be a solution for your question.

来源：https://stackoverflow.com/questions/51323748/setup-py-add-dependencies-required-for-installation

标签

python

setup.py

python-packaging