Question

How to check a deque’s length in python?

I don’t see they provide deque.length in Python…

http://docs.python.org/tutorial/datastructures.html

from collections import deque
queue = deque(["Eric", "John", "Michael"])

How to check the length of this deque?

and can we initialize like

queue = deque([])   #is this length 0 deque?

Answer 1

len(queue) should give you the result, 3 in this case.

Specifically, len(object) function will call object.__len__ method [reference link]. And the object in this case is deque, which implements __len__ method (you can see it by dir(deque)).

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queue= deque([])   #is this length 0 queue?

Yes it will be 0 for empty deque.