python-dependency-injector

Simple python dependency injector library.

Latest version: 0.1.0

The changelog can be found here.

How to use

There are 3 steps to use this library:

1. Create a Container.
2. Load the Container.
3. Inject a dependency.

API

More API content can be found here.

Examples

Simple injection

When a Factory provider is created, every time the provider's inject method is called, the Callable will be called.

from di.container import Container
from di.provider import Factory
from di.injector import Injector

container = Container(
    Factory[int](lambda: 42), # Injects the number 42
    Factory[str](lambda: "A text") # Injects a string
)

injector = Injector()
injector.load_container(container)

my_number = injector.inject(int) # my_number == 42
my_text = injector.inject(str) # my_text == "A text"

Singleton injection

When a Singleton provider is created, the Callable passed will only be called once and the result value will be cached.

from random import randint

from di.container import Container
from di.provider import Singleton
from di.injector import Injector

container = Container(
    Singleton[int](lambda: randint())
)

injector = Injector()
injector.load_container(container)

my_number = injector.inject(int) # Suppose the injected value is 42
my_number2 = injector_inject(int) # Will inject the same number

Providers with qualifiers

A qualifier is anything that can identify a Provider.

from di.container import Container
from di.provider import Fatory
from di.injector import Injector

container = Container(
    Factory[int](lambda: 1, "INITIAL VALUE"),
    Factory[int](lambda: 42, "ANSWER TO EVERYTHING")
)

injector = Injector()
injector.load_container(container)

first_value = injector.inject("INITIAL VALUE") # first_value == 1
second_value = injector.inject("ANSWER TO EVERYTHING") # second_value == 42

Overriding providers

When multiple Providers are created for the same data type, the last Provider to be loaded will override all other Providers.

from di.container import Container
from di.provider import Fatory
from di.injector import Injector

container_1 = Container(
    Factory[int](lambda: 1)
)

container_2 = Container(
    Factory[int](lambda: 99)
)

injector = Injector()
injector.load_containers(container_1, container_2)

int_value = injector.inject(int) # int_value == 99

Dependency with dependencies

You can inject dependencies in the Providers definitions.

from di.container import Container
from di.provider import Fatory
from di.injector import Injector

class MyDataClass:
    def __init__(self, name: str, age: int):
        self.name = name
        self.age = age

injector = Injector()

container = Container(
    Factory[int](lambda: 1),
    Factory[str](lambda: "John Doe"),
    Factory[MyDataClass](lambda: MyDataClass(name=injector.inject(str), age=injector.inject(int)))
)

injector.load_container(container)

my_obj = injector.inject(MyDataClass)
# my_obj.name == "John Doe"
# my_obj.age == 1