Fastest way to check if a value exists in a list

Question

What is the fastest way to know if a value exists in a list (a list with millions of values in it) and what its index is?

I know that all values in the list are uniqu

Answer 1

Or use __contains__:

sequence.__contains__(value)

Demo:

>>> l=[1,2,3]
>>> l.__contains__(3)
True
>>>