__init__.py

from flask import Flask

def create_app():
    app = Flask(__name__)
    app.config['SECRET_KEY'] = 'fdadjfaoef afdpp'

    from .views import views
    from .auth import auth

    app.register_blueprint(views,url_prefix='/')
    # app.register_blueprint(auth,url_prefix='/auth/') #What's different between both this here before every url it must /auth/ then what you want
    app.register_blueprint(auth,url_prefix='/')      #It will be / only no prefix-> before url
    return app