Summary

本章小结

• A loop is used to repeat code as many times as needed.
• We use a for loop when we know how many iterations the loop will do; we use a while loop when we don’t know how many iterations a loop will do.
• Python uses indentation to determine which lines of code go together.
• A dictionary is a mapping from keys (such as words) to values (such as their frequencies).
• We need to open a file before we can read from it.
• Once a file is open, we can use methods or a loop to read its lines.
• Some modules (such as csv and zipfile) come with Python and can be used by importing them.
• Other modules, such as matplotlib, need to be installed first before they can be imported and used.

• 循环用于根据需要重复执行代码多次。
• 当我们明确知道循环将执行的迭代次数时，使用 for 循环；而在不确定循环将执行多少次迭代时，则采用 while 循环。
• Python 通过缩进来判断哪些代码行应该组合在一起。
• 字典是从键（例如单词）到值（例如它们的频率）的映射。
• 我们必须先打开一个文件，才能开始从中读取数据。
• 文件打开后，我们可以使用方法或循环来逐行读取。
• 一些模块（如 csv 和 zipfile）是 Python 自带的，可以直接通过导入来使用。
• 其他模块，例如 matplotlib，需先安装之后才能导入和使用。