Kaprekar Constant

kaprekar.py

#!/usr/bin/python
import sys
def kaprekar_diff(n):
    nlist = list(str(n))
    if n < 1000:
        if len(nlist) == 1:
            nlist = nlist + list('000')
        elif len(nlist) == 2:
            nlist = nlist + list('00')
        elif len(nlist) == 3:
            nlist = nlist + list('0')
    maxn = int(''.join(sorted(nlist, reverse=True)))
    minn = int(''.join(sorted(nlist)))
    return maxn - minn

def find_kaprekar(n1):
    kpass = 1
    while kpass <= 7:
        n1 = kaprekar_diff(n1)
        if n1 == 6174:
            break
        else:
            kpass += 1
    return kpass

# main
start,end = 1000,10000

kaprekar_map = {}
for n in xrange(start,end):
    if n not in [1111,2222,3333,4444,5555,6666,7777,8888,9999]:
        kpass_out = find_kaprekar(n)
        print 'n=' + str(n) + ' pass=' + str(kpass_out)
        if kpass_out > 7:
            continue
        if kpass_out in kaprekar_map:
            kaprekar_map[kpass_out].append(n)
        else:
            kaprekar_map[kpass_out] = []
            kaprekar_map[kpass_out].append(n)

print '** Kaprekar number analysis ' + str(start) + '-' + str(end-1) + ' **'
for key in kaprekar_map.keys():
    print 'Bucket:' + str(key) + ', Numbers which require ' + str(key)+  ' iterations=>'+ str(len(kaprekar_map[key]))