Should I automatically install needed modules?

Question

I'm writing a program for my grandpa. Occasionally an update will require a new module that's not installed on his computer. I don't want to have to manually install new modules every time, but he's not tech savvy enough to figure it out himself.

Is it OK for me to check for ImportErrors and install a module from the error message? If not, what's the alternative?

Answer 1

This is the job of the package manager. In the case of Python: pip.

If you package the library you are building and specify its dependencies, your users (grandpa), will simply need to run:

$ pip install --upgrade <name-of-package>

to get the latest version you've released and all of its dependencies. If you don't want to publish your code online, pip can also install from local sources:

$ pip install zipped_package_emailed_to_grandpa.zip

or, if you really need to package this in a single (Python 3.4+) script, you could call pip from within:

#!/usr/bin/env python3

def main():
   ...

if __name__ == '__main__':
    import sys, subprocess
    dependencies = ['dep_1', 'dep_2']
    subprocess.call([sys.executable, '-m', 'pip', 'install'] + dependencies)
    import dep_1, dep_2
    main()

but this is definitely uncommon.