defaultdict的核心原理是它在初始化时接受一个工厂函数（factory function），这个函数用于生成默认值。当访问一个不存在的键时，defaultdict会调用这个工厂函数来生成默认值，并将其插入到字典中。这使得defaultdict在处理图算法、计数器等需要频繁检查键是否存在的场景时，比普通字典更加高效和简洁。

Once you know how to add and use a Python module, you will greatly extend the capabilities of the language. A Python module is an external class or set of functions that exist outside the main file of ...

Learn how to use Python’s async functions, threads, and multiprocessing capabilities to juggle tasks and improve the responsiveness of your applications. If you program in Python, you have most likely ...

The example files used here can be downloaded by clicking the file name: example1.txt, example1.csv, example1.xlsx. (For text format files, you can copy the content on the webpage and paste it into a ...