[Solved] Which of the following code snippets correctly shows the extension initialization pattern in Flask? — Ans: db = SQLAlchemy() def create_app(): app = Flask(__name__) db.init_app(app)... | Flask

Flask - Middleware and Extensions

Which of the following code snippets correctly shows the extension initialization pattern in Flask?

Adef create_app(): app = Flask(__name__) db = SQLAlchemy() return app

Bdef create_app(): app = Flask(__name__) db = SQLAlchemy(app) return app

Cdb = SQLAlchemy(app) def create_app(): app = Flask(__name__) return app

Ddb = SQLAlchemy() def create_app(): app = Flask(__name__) db.init_app(app) return app

Step-by-Step Solution

Solution:

Step 1: Identify correct extension creation
The extension instance should be created outside the factory without app argument.
Step 2: Check init_app usage inside factory
The extension is initialized with the app inside the factory using init_app(app).
Final Answer:
db = SQLAlchemy() outside factory, then db.init_app(app) inside factory. -> Option D
Quick Check:
Extension created outside + init_app inside factory = db = SQLAlchemy() def create_app(): app = Flask(__name__) db.init_app(app) return app [OK]

Quick Trick: Create extension globally, init inside factory with init_app [OK]

Common Mistakes:

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Which of the following code snippets correctly shows the extension initialization pattern in Flask?