Fastapi: [QUESTION] How can I get access to @app in a different file from main.py?

[RenanAlonkin]

Hello there,

Description

I have a middleware in my application, but, it is gigantic, and I want to move it to a different file. I would like to know if it is possible to access @app in a file that is not my main.py.

My main.py looks something like this:

import uvicorn
from fastapi import Depends, FastAPI, Header, HTTPException
from routers.supply_change import predict

app = FastAPI(title=title, description=description,
              version=version, docs_url=docs_url, redoc_url=redoc_url)

@app.middleware("http")
async def add_process_time_header(request: Request, call_next):
    # Do some stuff
    response = await call_next(request)
    # Do some stuff
    return response

app.include_router(predict.router)

but I want something like this:

• main.py

import uvicorn
from fastapi import Depends, FastAPI, Header, HTTPException
from routers.supply_change import predict

app = FastAPI(title=title, description=description,
              version=version, docs_url=docs_url, redoc_url=redoc_url)

app.include_router(predict.router)

• middleware.py

@app.middleware("http")
async def add_process_time_header(request: Request, call_next):
    # Do some stuff
    response = await call_next(request)
    # Do some stuff
    return response

[sm-Fifteen]

You usually want to do it the other way around: Define a middleware function or class in a separate file, and then import that in your main where it will be attached to your app.

The decorator syntax for middlewares is equivalent to app.add_middleware(BaseHTTPMiddleware, dispatch=add_process_time_header), so what you should be doing is:

import uvicorn
from fastapi import Depends, FastAPI, Header, HTTPException
from routers.supply_change import predict

from starlette.middleware import BaseHTTPMiddleware
from .middleware import add_process_time_header

app = FastAPI(title=title, description=description,
              version=version, docs_url=docs_url, redoc_url=redoc_url)

app.add_middleware(BaseHTTPMiddleware, dispatch=add_process_time_header)

app.include_router(predict.router)

[RenanAlonkin]

I did what you said, and it looks sooooo clean, thanks!

[tiangolo]

Thanks for the help here @sm-Fifteen ! :clap: :bow:

Thanks for reporting back and closing the issue @RenanAlonkin :+1: