And I want you to get used to this, that colon is important, it identifies the start, and then the set of indented things identify all the things at the same level, and when we reset back to the previous level, that's when we go back to where we were.

我希望大家熟悉这个结构，冒号很重要，它定义了开始的地方，然后缩进号代表着,同样一层的对象，当我们到了，不缩进的地方的时候，也就到了以前的状态。

麻省理工公开课 - 计算机科学及编程导论课程节选