Using the app context in a flask blueprint

app.py

from flask import Flask

from blueprint import sample

app = Flask(__name__)
app.register_blueprint(sample)
app.config['SOMETHING'] = 'something'

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

blueprint.py

from flask import Blueprint, current_app

sample = Blueprint('sample', __name__)


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

Run python app.py and visit http://localhost:5000/, there you will see something.