"""
Author: Lloyd Moore
Usage:
print perm("01", 2)
> ["00", "01", "10", "11"]
print perm("abcd", 2)
> [ 'aa', 'ab', 'ac', 'ad',
'ba', 'bb', 'bc', 'bd',
'ca', 'cb', 'cc', 'cd',
'da', 'db', 'dc', 'dd' ]
"""
def perm(chars, m, wrd="", wrds=[]):
if len(wrd) == m: return wrd
for i in range(0, len(chars)):
w = perm(chars, m, wrd+chars[i])
if type(w) == type(""): wrds.append(w)
return wrds