demitri / python_module_autoinstaller

A customization of your Python installation that will automatically install modules you need.

Automatically Install Missing Python Modules

This is a hack developed at dotAstronomy 2019 that will attempt to install Python modules that are imported from a script you run, but are missing from your installation. Instead of getting the usual

ModuleNotFoundError: No module named 'x'

the function will attempt to install the missing package.

This patch works for Python scripts run on the command line as well as the interactive interpreter. When running a script with a missing module the script will need to be rerun after the installation; this is not needed for the interactive interpreter.

Installation Instructions

1. In your terminal, start Python.

2. Enter the following:

   import site
   print(site.getusersitepackages())
   

3. Open (or cd into) the directory returned. It's possible that you may need to create parts of the path.

4. Open the file sitecustomize.py. If it's not there, you will need to create it.

5. Paste the contents of the file in this repository called python_package_autoinstall.py.

6. Important! Make sure to set the configuration options (see below) specific to your installation.

Configuration Options

Some variables should be set to reflect your Python environment and preferences. These are at the top of the function handle_import_exception:

• ask_to_install : Set to True if you want to be prompted whether to install package that wasn't found; False to try to immediately try to install it.
• uses_sudo : Set to True if your Python installation requires sudo to install packages via pip; set to False if your Python is installed in a user-readable location. In other words, if you normally install packages with sudo pip install xxx, set this to True.

How It Works

Python has a mechanism to let you set what code is called when certain events occur. This code attaches its own function to the exception hook; in other words, every time an exception is raised, our code will be called.

Our function checks the name of the exception and only does anything if the exception is named ModuleNotFoundError. It then gets the name of the package that the script tried to import and run pip install <package> on the command line for you.

Caveats

The function attempts to install missing packages using pip. If you have a different package manager, e.g. Anaconda's conda, this is will not be used. In general, this is not a problem. Supporting conda would be a great update to the code!