打印列表，子列表内出现三个点 [英] Printed a list, three dots appeared inside sublists

问题描述

我打印出列表的内容，并得到以下输出:

I printed out the contents of a list, and i got the following output:

[[...], [...], [...], [...], [...], [...]]

这些奇怪的点是什么?

我使用了python 2.7.3

I used python 2.7.3

推荐答案

可能是您不小心建立了一个包含对自身的引用(或此处有很多引用)的列表:

Probably you accidentally built a list containing a reference to itself (or here, lots of references):

>>> a = ['x']
>>> a
['x']
>>> a[0] = a
>>> a
[[...]]

使用了三个点，以使字符串表示不会在递归中被淹没.您可以使用 id 和 is 运算符进行验证:

The three dots are used so that the string representation doesn't drown in recursion. You can verify this by using id and the is operator:

>>> id(a)
165875500
>>> id(a[0])
165875500
>>> a is a[0]
True

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