Response Cookies

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Use a Response parameter

You can declare a parameter of type Response in your path operation function.

And then you can set cookies in that temporal response object.

from fastapi import FastAPI, Response
app = FastAPI()
@app.post("/cookie-and-object/")
def create_cookie(response: Response):
    response.set_cookie(key="fakesession", value="fake-cookie-session-value")
    return {"message": "Come to the dark side, we have cookies"}

And then you can return any object you need, as you normally would (a dict, a database model, etc).

And if you declared a response_model, it will still be used to filter and convert the object you returned.

FastAPI will use that temporal response to extract the cookies (also headers and status code), and will put them in the final response that contains the value you returned, filtered by any response_model.

You can also declare the Response parameter in dependencies, and set cookies (and headers) in them.

Return a Response directly

You can also create cookies when returning a Response directly in your code.

To do that, you can create a response as described in Return a Response Directly.

Then set Cookies in it, and then return it:

from fastapi import FastAPI
from fastapi.responses import JSONResponse
app = FastAPI()
@app.post("/cookie/")
def create_cookie():
    content = {"message": "Come to the dark side, we have cookies"}
    response = JSONResponse(content=content)
    response.set_cookie(key="fakesession", value="fake-cookie-session-value")
    return response

Tip

Have in mind that if you return a response directly instead of using the Response parameter, FastAPI will return it directly.

So, you will have to make sure your data is of the correct type. E.g. it is compatible with JSON, if you are returning a JSONResponse.

And also that you are not sending any data that should have been filtered by a response_model.

More info

Technical Details

You could also use from starlette.responses import Response or from starlette.responses import JSONResponse.

FastAPI provides the same starlette.responses as fastapi.responses just as a convenience for you, the developer. But most of the available responses come directly from Starlette.

And as the Response can be used frequently to set headers and cookies, FastAPI also provides it at fastapi.Response.

To see all the available parameters and options, check the documentation in Starlette.