Flask: How to use app context inside blueprints?

Question

I'm learning flask and python and cannot wrap my head around the way a typical flask application needs to be structured.

I need to access the app config from inside blueprint. Something like this

#blueprint.py
from flask import Blueprint

sample_blueprint = Blueprint("sample", __name__)

# defining a route for this blueprint
@sample_blueprint.route("/")
def index():
     # !this is the problematic line
     # need to access some config from the app
     x = app.config["SOMETHING"]
     # how to access app inside blueprint?

If importing app in blueprint is the solution, will this not result in circulat imports? i.e importing blueprint in app, importing app in blueprints?

Answer 1

From the docs about appcontext:

The application context is what powers the current_app context local

Applied to your example:

from flask import Blueprint, current_app

sample = Blueprint('sample', __name__)

@sample.route('/')
def index():
    x = current_app.config['SOMETHING']

For reference here is a small gist I put together, as mentioned in the comments.

Answer 2

In your app - when registering the blueprint - you need to push the context manually.

Refer to the snippet below and notice how the call-out to the init_db function is wrapped with the application context - the with ensures that the context is destroyed upon completion of your task.

def create_app():
    app = Flask(__name__)

    with app.app_context():
        init_db()

    return app

Source