Circular Reference with python lists

问题

Can someone explain this?

>>> x=x[0]=[0]
>>> x
[[...]]
>>> x is x[0]
True
>>> x[0][0][0][0][0][0][0]
[[...]]
>>> x in x
True

what is [...]?

回答1:

That's just Python telling you that you have a circular reference; it's smart enough not to enter an infinite loop trying to print it out.

回答2:

It's output by the method responsible for generating the representation of the structure. It represents a recursive structure, elided since it can be nested infinitely.

回答3:

iPython will do this:

[<Recursion on list with id=38505216>]

It's the same thing; the interpreter telling you that you have a recursive data structure.

来源：https://stackoverflow.com/questions/4196329/circular-reference-with-python-lists