how to sort by 2 keys for list in python3

sort_2key.py

import functools

def sorted_by(a,b):
    if a[0] == b[0]:
        return a[1] - b[1]
    else:
        return a[0] - b[0]

cmp = functools.cmp_to_key(sorted_by)

a = [[2,0],[1,123],[1,24242],[1,0],[3,0]]
a.sort(key = cmp)
# a = [[1, 0], [1, 123], [1, 24242], [2, 0], [3, 0]]