20

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...

sorin
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    How about this solution: http://stackoverflow.com/questions/12332975/installing-python-module-within-code – Andrei Kaigorodov Jun 24 '13 at 09:09
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    I think this would be a very undesirable coding practice outside of the setup script. I (as I would guess most people) would not like/trust any program that I run that changes my environment. Tools like pip and virtualenv are specifically there so that the "user" has control of what package are installed down to which version. Not an expert on distutils but I know that it has facilities to list prerequisite requirements for any package. If it is only for your own use you could probably munge a bit of that code. – Joop Jun 24 '13 at 09:15
  • Thanks you guys, it works perfectly. As a note, that's a good solution for standalone scripts, not modules/packages. – sorin Jun 24 '13 at 09:52

4 Answers4

26

Updated for newer pip version (>= 10.0):

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

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.

Koterpillar
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sorin
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    This worked for me to install `boto3` on the PythonAnywhere service. Seems like pip.main() is just a wrapper around the command line tool, rather than offering an API. Kind ugly, but functional I suppose. I was getting an "access denied" message, until I added `--user`. –  Aug 11 '15 at 18:19
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    I've updated this answer for the newer pip versions. Hopefully it's OK as it doesn't change the spirit of the answer, just the location of the method. – Koterpillar Jul 29 '19 at 06:24
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    As the leading-underscore name implies, `_internal` is not meant to be used this way, and could disappear from future versions of `pip` at a moment's notice (or its interface could radically change without warning or documentation). – Karl Knechtel Jan 19 '23 at 08:04
10

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
Phoenix
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3

Do not use pip.main or pip._internal.main.

Quoting directly from the official documentation (boldface emphasis and editing comments mine, italics theirs):

As noted previously, pip is a command line program. While it is... available from your Python code via import pip, you must not use pip’s internal APIs in this way. There are a number of reasons for this:

  1. The pip code assumes that [it] is in sole control of the global state of the program. pip manages things like... without considering the possibility that user code might be affected.
  2. pip’s code is not thread safe. If you were to run pip in a thread, there is no guarantee that either your code or pip’s would work as you expect.
  3. pip assumes that once it has finished its work, the process will terminate... calling pip twice in the same process is likely to have issues.

This does not mean that the pip developers are opposed in principle to the idea that pip could be used as a library - it’s just that this isn’t how it was written, and it would be a lot of work to redesign the internals for use as a library [with a] stable API... And we simply don’t currently have the resources....

...[E]verything inside of pip is considered an implementation detail. Even the fact that the import name is pip is subject to change without notice. While we do try not to break things as much as possible, all the internal APIs can change at any time, for any reason....

...[I]nstalling packages into sys.path in a running Python process is something that should only be done with care. The import system caches certain data, and installing new packages while a program is running may not always behave as expected....

Having said all of the above[:] The most reliable approach, and the one that is fully supported, is to run pip in a subprocess. This is easily done using the standard subprocess module:

subprocess.check_call([sys.executable, '-m', 'pip', 'install', 'my_package'])

It goes on to describe other more appropriate tools and approaches for related problems.

Karl Knechtel
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1

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'])
Casey
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