necessary 0.1.1

Python package to enforce optional dependencies

Necessary

Python package to enforce optional dependencies.

How to Use

Simply use necessary.necessary to conditionally import a module.

from necessary import necessary

if necessary('torch'):
    # this will raise an 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_check:

try:
    # assuming torch is not installed
    necessary('torch')
except ImportError:
    out = necessary('torch', soft_check=True)
    print(out)  # this prints False

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

if necessary('torch', min_version='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

Issues with Pylance

If you use Pylance language server with Pyright, Pylance might complain that the imported module might be out of scope. As a workaround, combine necessary with TYPE_CHECKING:

from typing import TYPE_CHECKING
from necessary import necessary

if necessary('torch') or TYPE_CHECKING:
    import torch