Let's say you want to create an API that has 2 or more endpoints. In this scenario, it almost always make sense to use APIRouter include_router so that each endpoint has it's own dedicated file as a way to create a clean, well organized app. For example, let's say your app has the following structure.

├── main.py
├── api (directory)
│   ├── __init__.py
│   ├── foo.py
│   ├── bar.py

main.py could have something like this.

from fastapi import FastAPI
from api import foo, bar

app = FastAPI()

app.include_router(foo.router)
app.include_router(bar.router)

valid_endpoints = []
valid_endpoints += ['/api/foo']
valid_endpoints += ['/api/bar']

@app.post("/{rest_of_path:path}")
async def catch_all(rest_of_path: str):

  if f"/{rest_of_path}" not in valid_endpoints:
    message = f"/{rest_of_path} is NOT a valid endpoint. The valid endpoints are: {valid_endpoints}"
  else:
    message = f"/{rest_of_path} is a valid endpoint. The valid endpoints are: {valid_endpoints}"

  return {"message": message}

api/__init__.py would be an empty file.

app/foo.py could have something like this.

from fastapi import APIRouter


router = APIRouter()



@router.post("/api/foo")
async def foo():

  return { "message": "Hello from foo" } 

app/bar.py could have something like this.

from fastapi import APIRouter

router = APIRouter()

@router.post("/api/bar")
async def bar():
  return { "message": "Hello from bar" }