Providers help to assemble the objects. They create objects and inject the dependencies.

Each provider is a callable. You call the provider like a function when you need to create an object. Provider retrieves the underlying dependencies and inject them into the created object. It causes the cascade effect that helps to assemble object graphs. See Factory, Singleton, Callable and other provider docs below.

├──> provider2()
├──> provider3()
│    │
│    └──> provider4()
└──> provider5()
     └──> provider6()

Another providers feature is an overriding. You can override any provider with another provider. This helps in testing. This also helps in overriding API clients with stubs for the development or staging environment. See the example at Provider overriding.

If you need to inject not the whole object but the parts see Injecting provided object attributes, items, or call its methods.

To create a new provider see Creating a custom provider.

Providers module API docs - dependency_injector.providers