Flask Error Handling: Custom Exceptions and Logging

Error handling in Flask is crucial for application stability and user experience. This article introduces the core methods of error handling in Flask: ### 1. Default Error Handling Using the `@app.errorhandler(code_or_exception)` decorator, you can customize responses for status codes such as 404 and 500. For example, return a friendly message like "The page is lost". In production environments, debug mode should be disabled to prevent exposing stack traces. ### 2. Custom Exceptions Define exception classes (e.g., `UserNotFoundError`) to encapsulate business errors (e.g., user not found). Use `raise` to proactively throw these exceptions and `@app.errorhandler` to catch them, enabling modular error handling. ### 3. Logging Leverage Python’s `logging` module to configure file logging (with size limits and backups). Differentiate error importance using `INFO`/`ERROR` levels, and record critical error information in production for troubleshooting. ### Conclusion Flask error handling should combine friendly prompts (to avoid crashes), precise error location (via logging), and modular design (custom exceptions). Key techniques include using `errorhandler`, encapsulating business exceptions, configuring file logging, and distinguishing log levels.