fastapi-better-di

What is this ?

fastapi-better-di is a utility that allows you to use DI in fastapi without Depends()

Installation

pip install fastapi_better_di

Examples

# app.py
import uvicorn
from fastapi import FastAPI
from fastapi_better_di.patcher.auto import is_pathed
# functions were patched immediately after import

assert is_pathed(), "Something went wrong"


class MyType:
    def __init__(self, value):
        self.value = value


app = FastAPI()
app.dependency_overrides[MyType] = lambda: MyType(123)


@app.get("/")
def handler(my_type: MyType):  # <- DI without `Depends()`
    assert my_type.value == 123
    return my_type


if __name__ == "__main__":
    uvicorn.run(app)

See all examples

Usage

1. Patching:

   • Auto patching: patches classes when importing:

     from fastapi_better_di.patcher.auto import is_pathed # The classes were patched immediately after import
     
     # To check if everything is OK, use assert
     assert is_pathed(), "Something went wrong"
     

   • Manual patching: you need to call patch() by yourself:

     from fastapi_better_di.patcher.manual import patch, is_pathed
     
     patch()
     
     # To check if everything is OK, use assert
     assert is_pathed(), "Something went wrong"
     

   • Examples

• IMPORTANT: You can still use = Depends() without a function as an argument, and it won't add unnecessary arguments to the swagger.

  • Related issue: fastapi issue

• IMPORTANT: The main app(FastAPI) and dependency_overrides must be initialized before importing routers!

How it works

fastapi-better-di simply patch the handler function and add = Depends(func) as the default argument