Python Microservices with FastAPI

4

Dependency Injection in FastAPI

Now that you have learned how to properly structure our project with Domain Driven Design, we are able to talk about a powerful pattern that will help us separate infrastructure logic from our services, making our code more maintainable and easier to test.

Dependency injection (DI) is a design pattern where objects receive their dependencies from external sources rather than creating them internally. Think instead of an endpoint handling authentication directly, the authentication service is injected into the endpoint. This is quite simple to state but has deep consequences on our code design as you’ll see.

By the end of this chapter, you will have mastered dependency injection patterns in FastAPI, enabling you ...