d2.py

digits2alpha = {'1':('1'),
    '2':('a','b','c'),
    '3':('d','e','f'),
    '4':('g','h','i'),
    '5':('j','k','l'),
    '6':('m','n','o'),
    '7':('p','q','r','s'),
    '8':('t','u','v'),
    '9':('w','x','y','z'),
    '0':('0')}

def strings(digitstring):
  if len(digitstring) < 2: 
    return digits2alpha[digitstring[0]];
  else:
    suffixes = strings(digitstring[1:])
    vals = []
    for prefix in digits2alpha[digitstring[0]]:
       for suffix in suffixes:
         vals.append(prefix+suffix)
    return vals

if __name__ == "__main__":
  z = strings('123')
  print "Z is ", z