How to install a missing python package from insid

问题:

Assuming that you already have pip or easy_install installed on your python distribution, I would like to know how can I installed a required package in the user directory from within the script itself.

From what I know pip is also a python module so the solution should look like:

try:
    import zumba
except ImportError:
    import pip
    # ... do "pip install --user zumba" or throw exception   <-- how?
    import zumba

What I am missing is doing "pip install --user zumba" from inside python, I don't want to do it using os.system() as this may create other problems.

I assume it is possible...

回答1:

Thanks to @Joop I was able to come-up with the proper answer.

try:
    import zumba
except ImportError:
    import pip
    pip.main(['install', '--user', 'zumba'])
    import zumba

One important remark is that this will work without requiring root access as it will install the module in user directory.

Not sure if it will work for binary modules or ones that would require compilation, but it clearly works well for pure-python modules.

Now you can write self contained scripts and not worry about dependencies.

回答2:

As of pip version >= 10.0.0, the above solutions will not work because of internal package restructuring. The new way to use pip inside a script is now as follows:

try: import abc
except ImportError:
    from pip._internal import main as pip
    pip(['install', '--user', 'abc'])
    import abc

回答3:

I wanted to note that the current accepted answer could result in a possible app name collision. Importing from the app namespace doesn't give you the full picture of what's installed on the system.

A better way would be:

import pip

packages = [package.project_name for package in pip.get_installed_distributions()]

if 'package' not in packages:
    pip.main(['install', 'package'])