"""Soundex algorithm
This program is part of "Dive Into Python", a free Python book for
experienced programmers. Visit http://diveintopython.org/ for the
latest version.
"""
__author__ = "Mark Pilgrim (mark@diveintopython.org)"
__version__ = "$Revision: 1.2 $"
__date__ = "$Date: 2004/05/06 21:36:36 $"
__copyright__ = "Copyright (c) 2004 Mark Pilgrim"
__license__ = "Python"
import string, re
charToSoundex = {"A": "9",
"B": "1",
"C": "2",
"D": "3",
"E": "9",
"F": "1",
"G": "2",
"H": "9",
"I": "9",
"J": "2",
"K": "2",
"L": "4",
"M": "5",
"N": "5",
"O": "9",
"P": "1",
"Q": "2",
"R": "6",
"S": "2",
"T": "3",
"U": "9",
"V": "1",
"W": "9",
"X": "2",
"Y": "9",
"Z": "2"}
isOnlyChars = re.compile('^[A-Za-z]+$').search
def soundex(source):
"convert string to Soundex equivalent"
# Soundex requirements:
# source string must be at least 1 character
# and must consist entirely of letters
if not isOnlyChars(source):
return "0000"
# Soundex algorithm:
# 1. make first character uppercase
source = source[0].upper() + source[1:]
# 2. translate all other characters to Soundex digits
digits = source[0]
for s in source[1:]:
s = s.upper()
digits += charToSoundex[s]
# 3. remove consecutive duplicates
digits2 = digits[0]
for d in digits[1:]:
if digits2[-1] != d:
digits2 += d
# 4. remove all "9"s
digits3 = re.sub('9', '', digits2)
# 5. pad end with "0"s to 4 characters
while len(digits3) < 4:
digits3 += "0"
# 6. return first 4 characters
return digits3[:4]
if __name__ == '__main__':
from timeit import Timer
names = ('Woo', 'Pilgrim', 'Flingjingwaller')
for name in names:
statement = "soundex('%s')" % name
t = Timer(statement, "from __main__ import soundex")
print name.ljust(15), soundex(name), min(t.repeat())
