0Status codes tell the client if a request worked or not. Controlling them helps your app communicate clearly.
from fastapi import FastAPI, status from fastapi.responses import JSONResponse app = FastAPI() @app.get("/items/{item_id}", status_code=status.HTTP_200_OK) async def read_item(item_id: int): return {"item_id": item_id} @app.post("/items/", status_code=status.HTTP_201_CREATED) async def create_item(item: dict): return item
Use status_code parameter in route decorators to set response status.
You can also return JSONResponse with a custom status code.
@app.get("/success", status_code=200) async def success(): return {"message": "OK"}
@app.post("/create", status_code=201) async def create(): return {"message": "Created"}
from fastapi.responses import JSONResponse @app.get("/custom") async def custom_status(): return JSONResponse(content={"error": "Not found"}, status_code=404)
This FastAPI app has two endpoints. The GET endpoint returns 200 if the item exists or 404 if not. The POST endpoint returns 201 when an item is created.
from fastapi import FastAPI, status from fastapi.responses import JSONResponse app = FastAPI() @app.get("/items/{item_id}", status_code=status.HTTP_200_OK) async def read_item(item_id: int): if item_id == 0: return JSONResponse(content={"error": "Item not found"}, status_code=status.HTTP_404_NOT_FOUND) return {"item_id": item_id, "name": "Sample Item"} @app.post("/items/", status_code=status.HTTP_201_CREATED) async def create_item(item: dict): return {"message": "Item created", "item": item}
Use status module constants for readability, like status.HTTP_404_NOT_FOUND.
Returning a JSONResponse lets you set status codes dynamically inside the function.
Always choose the right status code to help clients understand your API responses.
Status codes show if a request worked or failed.
Set status codes using status_code in route decorators or by returning JSONResponse.
Use standard codes like 200, 201, 404 for clear communication.
status_code in a FastAPI route?status_code in FastAPIstatus_code in a route tells the client what happened with their request.status_code directly in the route decorator.status_code=201 in the decorator. @app.post('/items')
def create_item():
status_code = 201
return {'message': 'Created'} wrongly assigns inside function without effect. @app.post('/items')
def create_item():
return {'message': 'Created'}, 201 returns a tuple which FastAPI does not accept. @app.post('/items')
def create_item():
return JSONResponse({'message': 'Created'}, status=201) uses JSONResponse but with wrong parameter name (status instead of status_code).from fastapi import FastAPI
from fastapi.responses import JSONResponse
app = FastAPI()
@app.get('/data')
async def get_data():
return JSONResponse(content={'info': 'ok'}, status_code=202)JSONResponse with status_code=202.from fastapi import FastAPI
app = FastAPI()
@app.get('/item/{item_id}', status_code=404)
async def read_item(item_id: int):
return {'item_id': item_id}status_code=404 in the decorator makes every response return 404 status regardless of logic.status_code=201 in decorator sets default success code. Raising HTTPException sends error with desired status.status_code=201 in decorator and raise HTTPException(status_code=400) if username missing uses decorator for success and exception for error, which is correct. Set status_code=201 in decorator and return JSONResponse with status_code=400 inside function mixes decorator and response status codes causing confusion. Return a tuple with data and status code 201 or 400 returning tuple is invalid in FastAPI. Set status_code=400 in decorator and return 201 in response body sets wrong default status code and misuses response body.Pass the test and this pattern moves unknown strong while earning +1 Grip toward your certificate.