python-injection 0.5.0

Fast and easy dependency injection framework.

Basic usage

Create an injectable

If you wish to inject a singleton, use singleton decorator.

from injection import singleton

@singleton
class Singleton:
    """ class implementation """

If you wish to inject a new instance each time, use injectable decorator.

from injection import injectable


@injectable
class Injectable:
    """ class implementation """

Inject an instance

To inject one or several instances, use inject decorator. Don't forget to annotate type of parameter to inject.

from injection import inject

@inject
def my_function(instance: Injectable):
    """ function implementation """

If inject decorates a class, it will be applied to the __init__ method. Especially useful for dataclasses:

from dataclasses import dataclass

from injection import inject

@inject
@dataclass
class DataClass:
    instance: Injectable = ...

Inheritance

In the case of inheritance, you can use the decorator parameter on to link the injection to one or several other classes.

Warning: if the child class is in another file, make sure that file is imported before injection. See load_package function.

Example with a reference class:

from injection import singleton

class A:
    ...

@singleton(on=A)
class B(A):
    ...

Example with several reference classes:

from injection import singleton

class A:
    ...

class B(A):
    ...

@singleton(on=(A, B))
class C(B):
    ...

Recipes

A recipe is a function that tells the injector how to construct the instance to be injected. It is important to specify the return type annotation when defining the recipe.

from injection import singleton

@singleton
def my_recipe() -> Singleton:
    """ recipe implementation """

Auto inject

By default, injectable and singleton decorators will automatically apply @inject to the decorated class or function. To disable it, set the auto_inject parameter to False.

from injection import singleton

@singleton(auto_inject=False)
class Singleton:
    """ class implementation """