Python package to enforce optional dependencies
Project description
Necessary
Python package that can be used to enforce optional dependencies are installed when a module is imported. Necessary stands for "Now Ensures Correct Existence of Select Software, or Add Resource Yourself!"
Necessary is available on PyPI, and can be installed with the following command:
pip install necessary
How to Use
As Context Manager
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 Python's requirements syntax:
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, or combine multiple requirements:
with necessary(['torch>=1.12.0', 'numpy>=1.20,<1.25']):
# 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
As Function or Class Decorator
You can also use necessary
as a function or class decorator:
from necessary import Necessary
# decorating a function
@Necessary('torch')
def my_function():
import torch
# decorating a class
@Necessary('torch')
class MyClass:
def __init__(self):
import torch
All of the same functionality is available in the decorator form as in the context manager form.
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