Flask Applications: `flask run` vs. `python sample.py`, Which One Should You Choose?

Running Flask Applications: A Detailed Guide

When embarking on a Flask application development journey, it's essential to understand the correct approach to starting your server. The Flask documentation presents two commands: flask -a sample run and python3.4 sample.py. While both methods effectively initiate the application, there are distinct differences between them.

The flask Command

The flask command provides a command-line interface (CLI) specifically designed for interacting with Flask applications. It offers various commands, including flask run, which is the recommended choice for starting the development server.

$ flask --app sample --debug run

This command leverages the --app option to indicate your app, identifying it either by import name or file name. It automatically detects an app instance or an app factory named create_app. Employ the --debug option to run the application in debug mode.

The python sample.py Command

The python sample.py command executes the specified Python file and sets name == "__main__". If the main block calls app.run(), the development server will be activated. If your application utilizes an app factory, you have the flexibility to instantiate an app instance during this execution.

if __name__ == "__main__":
    app = create_app()
    app.run(debug=True)

Which Command Should You Use?

The flask run command is highly recommended for starting Flask applications. It offers a consistent and convenient approach, particularly when using app factories. While the python sample.py command can also initiate your application, it is more suited to specific scenarios where direct control over the app instance is desired.

Conclusion

Choosing the appropriate command to start your Flask application is crucial for smooth and efficient development. The flask command provides an optimized CLI experience, while the python sample.py command offers greater flexibility. By understanding the differences between these two methods, you can select the one that best aligns with your specific development requirements.

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