Specifics of List Membership

Question

How does Python (2.6.4, specifically) determine list membership in general? I\'ve run some tests to see what it does:

def main():
    obj = fancy_obj(arg=\'         


        

Answer 1

Python is using the (equivalent of) the == operator. If the fancy_obj class does not define __eq__ (or the crufty old __cmp__, still supported for backwards compatibility) then equality, ==, "falls back" to identity, is, and that appears to be what's happening here.

The relevant docs are here, and I quote:

x in s True if an item of s is equal to x, else False

and "equal to" means == is true.