So in fact what happens inside of an object-oriented system, and particularly in init Python's object-oriented system, is the following.

面向对象系统的内部,尤其是在Python的面向，对象系统的内部的过程,就是如下的，当我们调用，它会去创建一个实例。

麻省理工公开课 - 计算机科学及编程导论课程节选

I just doubled the indentation each time so you can see it. So each successive call, notice what's happening. The argument is getting reduced. And we're going another level in. When we get down to this point, we're calling it with just a string of length one.

因此每次成功调用注意它的过程,我们的命题不断简化，而且我们不断深入嵌套,当我们走到这一步的时候,我们就是在调用它处理，仅有一个元素的字符串了。

麻省理工公开课 - 计算机科学及编程导论课程节选