Instruction: What does the `flask run` command do, and when would you use it?
Context: This question assesses the candidate's familiarity with running Flask applications using the Flask Command Line Interface.
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To elaborate, when you execute the flask run command in the terminal within the root directory of a Flask project, Flask looks for the application instance to serve to the web. This instance is specified by the FLASK_APP environment variable. If this variable isn't explicitly set, Flask will default to attempting to detect the app instance automatically, usually looking for a file named app.py or wsgi.py.
The command essentially instructs Flask to start a local development server. This server is built-in, meaning you don't need to configure a web server like Apache or Nginx for development testing. The development server is lightweight and designed...