Soundex is *one* particular algorithm for approximate string matching.
It is optimised for matching Anglo-American names (like Smith/Smythe),
and is considered to be quite old and obsolete for all but the most
trivial applications -- or so I'm told.
Soundex will not match arbitrary changes -- it will match both cat and
cet, but it won't match cat and mat.
A more sophisticated approximate string matching algorithm will use the
Levenshtein distance. You can find a Useless implementation here:
http://www.uselesspython.com/download.php?script_id=108
Given a function levenshtein(s1, s2) that returns the distance between
two strings, you could use it for approximate matching like this:
def approx_matching(strlist, target, dist=1):
"""Matches approximately strings in strlist to
a target string.
Returns a list of strings, where each string
matched is no further than an edit distance of
dist from the target.
"""
found = []
for s in strlist:
if levenshtein(s, target) <= dist:
found.append(s)
return s