This is the job of the package manager. In the case of Python: [`pip`](https://pip.pypa.io/en/stable/).

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`