One-line Soundex code generator using functional programming and python hackery

soundex.py

from functools import reduce # Needed for Python 3.x
from operator import add

def soundex(letters, duplicates=False, initial=True, size=4,
            sounds=[('aeiouyhw', ''), ('bfpv', '1'), ('cgjkqsxz', '2'), ('dt', '3'), ('l', '4'), ('mn', '5'), ('r', '6')]):
    return '0'*size if not len(letters) else ((letters[0] if initial else '') +
        reduce(lambda stack, next: stack+next if stack[-1:] != next or duplicates else stack,
            map(lambda letter: reduce(add, (val for (key,val) in sounds if letter in key), ''), letters[1:]), ''))[:size if size else None].ljust(size, '0')