How Can I Effectively Debug Errors in My Flask Application?

Troubleshooting Errors in Flask Applications

When errors arise in Flask applications, developers have multiple debugging options available:

1. Debug Mode

As of Flask 2.2, enabling debug mode provides an interactive traceback and console within the browser upon encountering an error. To activate this mode, run the following command:

flask --app example --debug run

Alternatively, you can set the FLASK_APP and FLASK_DEBUG environment variables.

2. Terminal Tracebacks

Regardless of debug mode status, tracebacks are always printed to the terminal running the server.

3. IDE Integration

IDEs like PyCharm and VS Code allow debugging with breakpoints. Point the run configuration to app.run(debug=True, use_reloader=False) or use the venv/bin/flask script with the same options.

4. Terminal Debuggers

Use set_trace in the appropriate view to activate terminal debuggers such as pdb or pudb.

Avoidance Tips

To prevent debugging issues:

• Avoid excessive except blocks that silence errors.
• Flask handles exceptions by presenting the debugger or a 500 error and printing the traceback to the console.

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