Create Twitter login for FastAPI

An example of how to implement OAuth 1.0 clients in FastAPI.

FastAPI is a modern, fast (high-performance), web framework for building APIs with Python 3.6+ based on standard Python type hints.

It is created on top of Starlette. A FastAPI app is basically a Starlette app, that is why you can just use Authlib Starlette integration to create OAuth clients for FastAPI.

Create OAuth client

A typical OAuth client for Starlette or FastAPI:

from authlib.integrations.starlette_client import OAuth

from starlette.config import Config



config = Config('.env')  # read config from .env file

oauth = OAuth(config)

We will create a twitter login example for FastAPI. Like all web frameworks integrations in Authlib, we need to register a remote:

oauth.register(

    name='twitter',

    api_base_url='https://api.twitter.com/1.1/',

    request_token_url='https://api.twitter.com/oauth/request_token',

    access_token_url='https://api.twitter.com/oauth/access_token',

    authorize_url='https://api.twitter.com/oauth/authenticate',

)

We don't need to add client_id and client_secret here, because they are in .env file. You are not supposed to hard code them in the code in real products.

Implement login route

First, create a FastAPI application:

from fastapi import FastAPI

from starlette.middleware.sessions import SessionMiddleware



app = FastAPI()

app.add_middleware(SessionMiddleware, secret_key="secret-string")

We need this SessionMiddleware, because Authlib will use request.session to store temporary codes and states.

Next, the /login route will redirect us to Twitter website to grant access:

@app.route('/login')

async def login(request: Request):

    # absolute url for callback

    # we will define it below

    redirect_uri = request.url_for('auth')

    return await oauth.twitter.authorize_redirect(request, redirect_uri)

The above code will exchange request_token and redirect to Twitter website for you.

Handle authentication callback

When you grant access from Twitter website, twitter will redirect back to your given redirect_uri, which is request.url_for('auth'):

@app.route('/auth')

async def auth(request: Request):

    token = await oauth.twitter.authorize_access_token(request)

    url = 'account/verify_credentials.json'

    resp = await oauth.twitter.get(

        url, params={'skip_status': True}, token=token)

    user = resp.json()

    return user

The above code will exchange an access_token. You can use the token to access users' resources. In the above example, we are requesting the authenticated user's profile information.

Hint

You can register a Twitter OAuth Client at https://developer.twitter.com/en/apps. Remember to add the full auth url in Callback URL.

You can check the full example: https://github.com/authlib/demo-oauth-client/tree/master/fastapi-twitter-login.

Tip