how to compare a specific items on a list python code example

Example 1: python compare each item of one list

import itertools
for a, b in itertools.combinations(mylist, 2):
    compare(a, b)

Example 2: how to make every item compare the rest items of list in python

for i in range(len(mylist)):
    for j in range(i + 1, len(mylist)):
        compare(mylist[i], mylist[j])