[Solved] Why might this Flask application factory code cause a runtime error?def create_app(): app = Flask(__name__) @app.route('/home') def home(): return 'Welcome' return app app = create_app() app.run() | Flask

Flask - Ecosystem and Patterns

Why might this Flask application factory code cause a runtime error?

def create_app():
    app = Flask(__name__)
    @app.route('/home')
    def home():
        return 'Welcome'
    return app

app = create_app()
app.run()

AFlask app must be created globally, not inside a function

BDefining routes inside the factory function is not allowed

CReturning app before defining routes causes missing endpoints

DCalling app.run() outside the factory without checking __name__ == '__main__'

Step-by-Step Solution

Solution:

Step 1: Analyze app.run() usage
Calling app.run() directly executes the server immediately.
Step 2: Check for __main__ guard
Best practice is to call app.run() inside if __name__ == '__main__' block to avoid errors when importing.
Step 3: Evaluate other options
Defining routes inside factory is valid. Returning app after routes is correct. Creating app inside function is standard.
Final Answer:
Calling app.run() outside the factory without checking __name__ == '__main__' -> Option D
Quick Check:
Is app.run() guarded by __main__? No. [OK]

Quick Trick: Always guard app.run() with if __name__ == '__main__' [OK]

Common Mistakes:

MISTAKES

Thinking routes can't be inside factory
Assuming app must be global
Returning app before route definitions

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More Flask Quizzes

Why might this Flask application factory code cause a runtime error?

Step 1: Analyze app.run() usage

Step 2: Check for main guard

Step 3: Evaluate other options

Final Answer:

Quick Check:

Want More Practice?

Why might this Flask application factory code cause a runtime error?

Step 1: Analyze app.run() usage

Step 2: Check for __main__ guard

Step 3: Evaluate other options

Final Answer:

Quick Check:

Want More Practice?

Step 2: Check for main guard