Developing Flask Extensions: A Simple Custom Extension Example

Flask extensions serve as functional supplements to the lightweight web framework, offering modular and reusable components. Developing custom extensions allows for learning core Flask concepts. This article takes `flask_simple_timer` (for recording request processing time) as an example, outlining the development steps: 1. Extension package structure (including `__init__.py`); 2. Using the `before_request` hook to record the start time (stored in the `g` object) and the `after_request` hook to calculate and print the elapsed time. When using, bind it to the Flask application (e.g., initializing in `app.py`), and testing the route verifies the functionality (outputting logs upon access). Key knowledge points include Flask context (the `g` object), `before/after_request` hooks, and extension initialization via direct binding or the `init_app` method. The core idea involves modular encapsulation, hooks, and context management. Mastering this process enables deeper understanding of Flask mechanisms and enhanced practical skills in extension development.