How can I add python type annotations to the flask global context g?

Question

I have a decorator which adds a user onto the flask global context g:

class User:
    def __init__(self, user_data) -&         


        

Answer 1

You can annotate an attribute on a class, even if that class isn't yours, simply with a colon after it. For example:

g.user: User

That's it. Since it's presumably valid everywhere, I would put it at the top of your code:

from functools import wraps

from flask import Flask, g

app = Flask(__name__)


class User:
    def __init__(self, user_data) -> None:
        self.username: str = user_data["username"]
        self.email: str = user_data["email"]


# Annotate the g.user attribute
g.user: User


def login_required(f):
    @wraps(f)
    def wrap(*args, **kwargs):
        g.user = User({'username': 'wile-e-coyote',
                       'email': 'coyote@localhost'})

        return f(*args, **kwargs)

    return wrap


@app.route('/')
@login_required
def hello_world():
    return f'Hello, {g.user.email}'


if __name__ == '__main__':
    app.run()

That's it.