What does “…” means in a python def

Question

This might be a very stupid question but I can't understand what the three dots stands for in a python def . I was trying to comprehend the cost of the in operator in a deque object (from the collections module), so I navigated through the code and here's what I found:

I thought they mean the method will use the "upper" definition when called, but if I navigate to the overridden method I can't find nothing if not an abstract method in the Container class.. so I still don't get how the in operator works on a deque object.

Answer 1

You are looking at a .pyi stub file. Referring to this post , a stub file, as the name suggests, is only meant to describe the interface and not the implementation inside. Hence, ... in a Python def really means that this file is just a def and you cannot find the implementation here.

Regarding your question about the cost of in operator in deque , refer to https://wiki.python.org/moin/TimeComplexity

It mentions deque is represented internally as a doubly-linked list, and also mentions that in operator for a list has O(n) complexity. I don't think it being a doubly-linked list changes the time complexity, as you would still need to go through each element, ie, O(n).