radix_sort.py

#!/usr/bin/env python

def radix_sort(l):
    modulus, div = 10, 1
    while True:
        buckets = [[] for i in range(modulus)]
        for value in l:
            buckets[(value % modulus) / div].append(value)
        modulus, div = modulus * 10, div * 10
        if len(buckets[0]) == len(l):
            return buckets[0]
        l = []
        for x in buckets:
            for y in x:
                l.append(y)

random_data = [13, 8, 1992, 31, 3, 1993]
print radix_sort(random_data)

A bit more Pythonic.