python-injection 0.6.7

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 """

Note: If the class needs dependencies, these will be resolved when the instance is retrieved.

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 = ...

Note: Doesn't work with Pydantic BaseModel because the signature of the __init__ method doesn't contain the dependencies.

Get an instance

Example with get_instance function:

from injection import get_instance

instance = get_instance(Injectable)

Example with get_lazy_instance function:

from injection import get_lazy_instance

lazy_instance = get_lazy_instance(Injectable)
# ...
instance = ~lazy_instance

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 one class:

from injection import singleton

class A:
    ...

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

Example with several 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 """