Sort list of strings containing Null values with Nulls at the end

sort_null_last.py

#!/usr/bin/env python3

from locale import strcoll
from functools import cmp_to_key


def null_last_cmp(a, b):
    """Comparison function that rates non-Null values lower than Null"""
    if a is None:
        return 0 if b is None else 1
    return -1 if b is None else strcoll(a, b)


values = ["abc", None, "def"]

print(sorted(values, key=cmp_to_key(null_last_cmp)))
# => ['abc', 'def', None]