necessary 0.2.2

Python package to enforce optional dependencies

Necessary

Python package to enforce optional dependencies.

Install with:

pip install necessary

How to Use

Simply use necessary.necessary to get a context manager import a module.

from necessary import necessary

with necessary('torch'):
    # this will raise a nicely written error if
    # torch is not installed
    import torch

If you want to just soft fail when a necessary module is not available (that is, have necessary return False), use soft:

try:
    # assuming torch is not installed
    necessary('torch')
except ImportError:
    out = necessary('torch', soft=True)
    assert out is False

If you want to request a minimum version, use min_version:

with necessary(('torch', '1.12.0')):
    # this will raise an error if
    # torch is not installed or if
    # the installed version is less than 0.12.0
    import torch

You can also check multiple packages in the same necessary call:

with necessary([('torch', '1.12.0'), 'numpy']):
    # this will raise an error if torch >= 1.12.0 or numpy are not installed
    import torch
    import numpy

Finally, we can customize the message that is raised if a necessary module is not installed; use {module_name} and {module_version} to insert the module name and version respectively.

with necessary('torch', message='I am missing {module_name}/{module_version}'):
    import torch