列表中的省略号 [...] 是什么意思? [英] What do ellipsis [...] mean in a list?

问题描述

我在玩 python.我在 IDLE 中使用了以下代码:

I was playing around in python. I used the following code in IDLE:

p  = [1, 2]
p[1:1] = [p]
print p

输出是:

[1, [...], 2]

这是什么[…]?有趣的是，我现在可以使用它作为一个列表列表，直到无穷大，即

What is this […]? Interestingly I could now use this as a list of list of list up to infinity i.e.

p[1][1][1]....

我可以随心所欲地写上面的内容，它仍然有效.

I could write the above as long as I wanted and it would still work.

• 它在内存中是如何表示的?
• 它有什么用?一些有用的案例示例会有所帮助.
• 任何指向官方文档的链接都会非常有用.

推荐答案

这意味着您创建了一个嵌套在其内部的无限列表，该列表无法打印.p 包含 p 包含 p ... 等等.[...] 符号是一种让您知道这一点的方式，并告知它无法表示！看看@6502 的回答，可以看到一张很好的图片，展示了正在发生的事情.

It means that you created an infinite list nested inside itself, which can not be printed. p contains p which contains p ... and so on. The [...] notation is a way to let you know this, and to inform that it can't be represented! Take a look at @6502's answer to see a nice picture showing what's happening.

现在，关于编辑后的三个新项目:

Now, regarding the three new items after your edit:

• 这个答案似乎涵盖了它
• Ignacio 的链接描述了一些可能的用途
• 这更像是一个数据结构设计的话题，而不是编程语言，所以在 Python 的官方文档中不太可能找到任何参考

• This answer seems to cover it
• Ignacio's link describes some possible uses
• This is more a topic of data structure design than programming languages, so it's unlikely that any reference is found in Python's official documentation

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