Flask Error Handling: 404, 500 Errors and Custom Responses

In web development, encountering error pages or server internal errors is a common issue. Returning default error pages (e.g., "404 Not Found") directly can degrade user experience. Flask provides a flexible error handling mechanism, allowing custom error responses via the `@app.errorhandler` decorator to enhance user experience. By default, Flask returns plain-text prompts for 404 (Page Not Found) and detailed stack traces for 500 (Server Error), which are difficult for users to understand. With `@app.errorhandler`, custom responses can be defined for different error codes: - **404 Error**: Return a friendly HTML page like "Page Not Found" with a link to return to the homepage; - **500 Error**: Return a "Server is having a moment" message, also with a link to the homepage; - **API Scenarios**: Return JSON-formatted error messages, such as `{"status":"error","code":404,"message":"User not found"}`. The core is the `@app.errorhandler` decorator, which supports HTML or JSON error responses and can be flexibly adjusted according to project requirements. This not only prevents user attrition due to unclear error prompts but also facilitates debugging.