Complexity of list.index(x) in Python

Question

I\'m referring to this: http://docs.python.org/tutorial/datastructures.html

What would be the running time of list.index(x) function in terms of big O n

Answer 1

According to said documentation:

list.index(x)

Return the index in the list of the first item whose value is x. It is an error if there is no such item.

Which implies searching. You're effectively doing x in s but rather than returning True or False you're returning the index of x. As such, I'd go with the listed time complexity of O(n).