metaphone.py

File contents

#!python
#coding= utf-8
# This script implements the Double Metaphone algorythm (c) 1998, 1999 by Lawrence Philips
# it was translated to Python from the C source written by Kevin Atkinson (http://aspell.net/metaphone/)
# By Andrew Collins - January 12, 2007 who claims no rights to this work
# http://www.atomodo.com/code/double-metaphone/metaphone.py/view
# Tested with Pyhon 2.4.3
# Updated Feb 14, 2007 - Found a typo in the 'gh' section
# Updated Dec 17, 2007 - Bugs fixed in 'S', 'Z', and 'J' sections. Thanks Chris Leong!
# Updated June 25, 2010 - several bugs fixed thanks to Nils Johnsson for a spectacular
#	bug squashing effort. There were many cases where this function wouldn't give the same output
#	as the original C source that were fixed by his careful attention and excellent communication.
#	The script was also updated to use utf-8 rather than latin-1.
def dm(st) :
	"""dm(string) -> (string, string or None)
	returns the double metaphone codes for given string - always a tuple
	there are no checks done on the input string, but it should be a single	word or name."""
	vowels = ['A', 'E', 'I', 'O', 'U', 'Y']
	st = st.decode('utf-8', 'ignore')
	st = st.upper() # st is short for string. I usually prefer descriptive over short, but this var is used a lot!
	is_slavo_germanic = (st.find('W') > -1 or st.find('K') > -1 or st.find('CZ') > -1 or st.find('WITZ') > -1)
	length = len(st)
	first = 2
	st = ('-') * first + st + (' ' * 5)  # so we can index beyond the begining and end of the input string
	last = first + length -1
	pos = first # pos is short for position
	pri = sec = '' # primary and secondary metaphone codes
	#skip these silent letters when at start of word
	if st[first:first+2] in ["GN", "KN", "PN", "WR", "PS"] :
		pos += 1
	# Initial 'X' is pronounced 'Z' e.g. 'Xavier'
	if st[first] == 'X' :
		pri = sec = 'S' #'Z' maps to 'S'
		pos += 1
	# main loop through chars in st
	while pos <= last :
		#print str(pos) + '\t' + st[pos]
		ch = st[pos] # ch is short for character
		# nxt (short for next characters in metaphone code) is set to  a tuple of the next characters in
		# the primary and secondary codes and how many characters to move forward in the string.
		# the secondary code letter is given only when it is different than the primary.
		# This is just a trick to make the code easier to write and read.
		nxt = (None, 1) # default action is to add nothing and move to next char
		if ch in vowels :
			nxt = (None, 1)
			if pos == first : # all init vowels now map to 'A'
				nxt = ('A', 1)
		elif ch == 'B' :
			#"-mb", e.g", "dumb", already skipped over... see 'M' below
			if st[pos+1] == 'B' :
				nxt = ('P', 2)
			else :
				nxt = ('P', 1)
		elif ch == 'C' :
			# various germanic
			if (pos > (first + 1) and st[pos-2] not in vowels and st[pos-1:pos+2] == 'ACH' and \
			   (st[pos+2] not in ['I', 'E'] or st[pos-2:pos+4] in ['BACHER', 'MACHER'])) :
				nxt = ('K', 2)
			# special case 'CAESAR'
			elif pos == first and st[first:first+6] == 'CAESAR' :
				nxt = ('S', 2)
			elif st[pos:pos+4] == 'CHIA' : #italian 'chianti'
				nxt = ('K', 2)
			elif st[pos:pos+2] == 'CH' :
				# find 'michael'
				if pos > first and st[pos:pos+4] == 'CHAE' :
					nxt = ('K', 'X', 2)
				elif pos == first and (st[pos+1:pos+6] in ['HARAC', 'HARIS'] or \
				   st[pos+1:pos+4] in ["HOR", "HYM", "HIA", "HEM"]) and st[first:first+5] != 'CHORE' :
					nxt = ('K', 2)
				#germanic, greek, or otherwise 'ch' for 'kh' sound
				elif st[first:first+4] in ['VAN ', 'VON '] or st[first:first+3] == 'SCH' \
				   or st[pos-2:pos+4] in ["ORCHES", "ARCHIT", "ORCHID"] \
				   or st[pos+2] in ['T', 'S'] \
				   or ((st[pos-1] in ["A", "O", "U", "E"] or pos == first) \
				   and st[pos+2] in ["L", "R", "N", "M", "B", "H", "F", "V", "W", " "]) :
					nxt = ('K', 1)
				else :
					if pos > first :
						if st[first:first+2] == 'MC' :
							nxt = ('K', 2)
						else :
							nxt = ('X', 'K', 2)
					else :
						nxt = ('X', 2)
			#e.g, 'czerny'
			elif st[pos:pos+2] == 'CZ' and st[pos-2:pos+2] != 'WICZ' :
				nxt = ('S', 'X', 2)
			#e.g., 'focaccia'
			elif st[pos+1:pos+4] == 'CIA' :
				nxt = ('X', 3)
			#double 'C', but not if e.g. 'McClellan'
			elif st[pos:pos+2] == 'CC' and not (pos == (first +1) and st[first] == 'M') :
				#'bellocchio' but not 'bacchus'
				if st[pos+2] in ["I", "E", "H"] and st[pos+2:pos+4] != 'HU' :
					#'accident', 'accede' 'succeed'
					if (pos == (first +1) and st[first] == 'A') or \
					   st[pos-1:pos+4] in ['UCCEE', 'UCCES'] :
						nxt = ('KS', 3)
					#'bacci', 'bertucci', other italian
					else:
						nxt = ('X', 3)
				else :
					nxt = ('K', 2)
			elif st[pos:pos+2] in ["CK", "CG", "CQ"] :
				nxt = ('K', 'K', 2)
			elif st[pos:pos+2] in ["CI", "CE", "CY"] :
				#italian vs. english
				if st[pos:pos+3] in ["CIO", "CIE", "CIA"] :
					nxt = ('S', 'X', 2)
				else :
					nxt = ('S', 2)
			else : 
				#name sent in 'mac caffrey', 'mac gregor
				if st[pos+1:pos+3] in [" C", " Q", " G"] :
					nxt = ('K', 3)
				else :
					if st[pos+1] in ["C", "K", "Q"] and st[pos+1:pos+3] not in ["CE", "CI"] :
						nxt = ('K', 2)
					else : # default for 'C'
						nxt = ('K', 1)
		elif ch == u'Ç' :
			nxt = ('S', 1)
		elif ch == 'D' :
			if st[pos:pos+2] == 'DG' :
				if st[pos+2] in ['I', 'E', 'Y'] : #e.g. 'edge'
					nxt = ('J', 3)
				else :
					nxt = ('TK', 2)
			elif st[pos:pos+2] in ['DT', 'DD'] :
				nxt = ('T', 2)
			else :
				nxt = ('T', 1)
		elif ch == 'F' :
			if st[pos+1] == 'F' :
				nxt = ('F', 2)
			else :
				nxt = ('F', 1)
		elif ch == 'G' :
			if st[pos+1] == 'H' :
				if pos > first and st[pos-1] not in vowels :
					nxt = ('K', 2)
				elif pos < (first + 3) :
					if pos == first : #'ghislane', ghiradelli
						if st[pos+2] == 'I' :
							nxt = ('J', 2)
						else :
							nxt = ('K', 2)
				#Parker's rule (with some further refinements) - e.g., 'hugh'
				elif (pos > (first + 1) and st[pos-2] in ['B', 'H', 'D'] ) \
				   or (pos > (first + 2) and st[pos-3] in ['B', 'H', 'D'] ) \
				   or (pos > (first + 3) and st[pos-4] in ['B', 'H'] ) :
					nxt = (None, 2)
				else : 
					# e.g., 'laugh', 'McLaughlin', 'cough', 'gough', 'rough', 'tough'
					if pos > (first + 2) and st[pos-1] == 'U' \
					   and st[pos-3] in ["C", "G", "L", "R", "T"] :
						nxt = ('F', 2)
					else :
						if pos > first and st[pos-1] != 'I' :
							nxt = ('K', 2)
			elif st[pos+1] == 'N' :
				if pos == (first +1) and st[first] in vowels and not is_slavo_germanic :
					nxt = ('KN', 'N', 2)
				else :
					# not e.g. 'cagney'
					if st[pos+2:pos+4] != 'EY' and st[pos+1] != 'Y' and not is_slavo_germanic :
						nxt = ('N', 'KN', 2)
					else :
						nxt = ('KN', 2)
			# 'tagliaro'
			elif st[pos+1:pos+3] == 'LI' and not is_slavo_germanic :
				nxt = ('KL', 'L', 2)
			# -ges-,-gep-,-gel-, -gie- at beginning
			elif pos == first and (st[pos+1] == 'Y' \
			   or st[pos+1:pos+3] in ["ES", "EP", "EB", "EL", "EY", "IB", "IL", "IN", "IE", "EI", "ER"]) :
				nxt = ('K', 'J', 2)
			# -ger-,  -gy-
			elif (st[pos+1:pos+2] == 'ER' or st[pos+1] == 'Y') \
			   and st[first:first+6] not in ["DANGER", "RANGER", "MANGER"] \
			   and st[pos-1] not in ['E', 'I'] and st[pos-1:pos+2] not in ['RGY', 'OGY'] :
				nxt = ('K', 'J', 2)
			# italian e.g, 'biaggi'
			elif st[pos+1] in ['E', 'I', 'Y'] or st[pos-1:pos+3] in ["AGGI", "OGGI"] :
				# obvious germanic
				if st[first:first+4] in ['VON ', 'VAN '] or st[first:first+3] == 'SCH' \
				   or st[pos+1:pos+3] == 'ET' :
					nxt = ('K', 2)
				else :
					# always soft if french ending
					if st[pos+1:pos+5] == 'IER ' :
						nxt = ('J', 2)
					else :
						nxt = ('J', 'K', 2)
			elif st[pos+1] == 'G' :
				nxt = ('K', 2)
			else :
				nxt = ('K', 1)
		elif ch == 'H' :
			# only keep if first & before vowel or btw. 2 vowels
			if (pos == first or st[pos-1] in vowels) and st[pos+1] in vowels :
				nxt = ('H', 2)
			else : # (also takes care of 'HH')
				nxt = (None, 1)
		elif ch == 'J' :
			# obvious spanish, 'jose', 'san jacinto'
			if st[pos:pos+4] == 'JOSE' or st[first:first+4] == 'SAN ' :
				if (pos == first and st[pos+4] == ' ') or st[first:first+4] == 'SAN ' :
					nxt = ('H',)
				else :
					nxt = ('J', 'H')
			elif pos == first and st[pos:pos+4] != 'JOSE' :
				nxt = ('J', 'A') # Yankelovich/Jankelowicz
			else :
				# spanish pron. of e.g. 'bajador'
				if st[pos-1] in vowels and not is_slavo_germanic \
				   and st[pos+1] in ['A', 'O'] :
					nxt = ('J', 'H')
				else :
					if pos == last :
						nxt = ('J', ' ')
					else :
						if st[pos+1] not in ["L", "T", "K", "S", "N", "M", "B", "Z"] \
						   and st[pos-1] not in ["S", "K", "L"] :
							nxt = ('J',)
						else :
							nxt = (None, )
			if st[pos+1] == 'J' :
				nxt = nxt + (2,)
			else :
				nxt = nxt + (1,)
		elif ch == 'K' :
			if st[pos+1] == 'K' :
				nxt = ('K', 2)
			else :
				nxt = ('K', 1)
		elif ch == 'L' :
			if st[pos+1] == 'L' :
				# spanish e.g. 'cabrillo', 'gallegos'
				if (pos == (last - 2) and st[pos-1:pos+3] in ["ILLO", "ILLA", "ALLE"]) \
				   or ((st[last-1:last+1] in ["AS", "OS"] or st[last] in ["A", "O"]) \
				   and st[pos-1:pos+3] == 'ALLE') :
					nxt = ('L', '', 2)
				else :
					nxt = ('L', 2)
			else :
				nxt = ('L', 1)
		elif ch == 'M' :
			if st[pos+1:pos+4] == 'UMB' \
			   and (pos + 1 == last or st[pos+2:pos+4] == 'ER') \
			   or st[pos+1] == 'M' :
				nxt = ('M', 2)
			else :
				nxt = ('M', 1)
		elif ch == 'N' :
			if st[pos+1] == 'N' :
				nxt = ('N', 2)
			else :
				nxt = ('N', 1)
		elif ch == u'Ñ' :
			nxt = ('N', 1)
		elif ch == 'P' :
			if st[pos+1] == 'H' :
				nxt = ('F', 2)
			elif st[pos+1] in ['P', 'B'] : # also account for "campbell", "raspberry"
				nxt = ('P', 2)
			else :
				nxt = ('P', 1)
		elif ch == 'Q' :
			if st[pos+1] == 'Q' :
				nxt = ('K', 2)
			else :
				nxt = ('K', 1)
		elif ch == 'R' :
			# french e.g. 'rogier', but exclude 'hochmeier'
			if pos == last and not is_slavo_germanic \
			   and st[pos-2:pos] == 'IE' and st[pos-4:pos-2] not in ['ME', 'MA'] :
				nxt = ('', 'R')
			else :
				nxt = ('R',)
			if st[pos+1] == 'R' :
				nxt = nxt + (2,)
			else :
				nxt = nxt + (1,)
		elif ch == 'S' :
			# special cases 'island', 'isle', 'carlisle', 'carlysle'
			if st[pos-1:pos+2] in ['ISL', 'YSL'] :
				nxt = (None, 1)
			# special case 'sugar-'
			elif pos == first and st[first:first+5] == 'SUGAR' :
				nxt =('X', 'S', 1)
			elif st[pos:pos+2] == 'SH' :
				# germanic
				if st[pos+1:pos+5] in ["HEIM", "HOEK", "HOLM", "HOLZ"] :
					nxt = ('S', 2)
				else :
					nxt = ('X', 2)
			# italian & armenian
			elif st[pos:pos+3] in ["SIO", "SIA"] or st[pos:pos+4] == 'SIAN' :
				if not is_slavo_germanic :
					nxt = ('S', 'X', 3)
				else :
					nxt = ('S', 3)
			# german & anglicisations, e.g. 'smith' match 'schmidt', 'snider' match 'schneider'
			# also, -sz- in slavic language altho in hungarian it is pronounced 's'
			elif (pos == first and st[pos+1] in ["M", "N", "L", "W"]) or st[pos+1] == 'Z' :
				nxt = ('S', 'X')
				if st[pos+1] == 'Z' :
					nxt = nxt + (2,)
				else :
					nxt = nxt + (1,)
			elif st[pos:pos+2] == 'SC' :
				# Schlesinger's rule
				if st[pos+2] == 'H' :
					# dutch origin, e.g. 'school', 'schooner'
					if st[pos+3:pos+5] in ["OO", "ER", "EN", "UY", "ED", "EM"] :
						# 'schermerhorn', 'schenker'
						if st[pos+3:pos+5] in ['ER', 'EN'] :
							nxt = ('X', 'SK', 3)
						else :
							nxt = ('SK', 3)
					else :
						if pos == first and st[first+3] not in vowels and st[first+3] != 'W' :
							nxt = ('X', 'S', 3)
						else :
							nxt = ('X', 3)
				elif st[pos+2] in ['I', 'E', 'Y'] :
					nxt = ('S', 3)
				else :
					nxt = ('SK', 3)
			# french e.g. 'resnais', 'artois'
			elif pos == last and st[pos-2:pos] in ['AI', 'OI'] :
				nxt = ('', 'S', 1)
			else :
				nxt = ('S',)
				if st[pos+1] in ['S', 'Z'] :
					nxt = nxt + (2,)
				else :
					nxt = nxt + (1,)
		elif ch == 'T' :
			if st[pos:pos+4] == 'TION' :
				nxt = ('X', 3)
			elif st[pos:pos+3] in ['TIA', 'TCH'] :
				nxt = ('X', 3)
			elif st[pos:pos+2] == 'TH' or st[pos:pos+3] == 'TTH' :
				# special case 'thomas', 'thames' or germanic
				if st[pos+2:pos+4] in ['OM', 'AM'] or st[first:first+4] in ['VON ', 'VAN '] \
				   or st[first:first+3] == 'SCH' :
					nxt = ('T', 2)
				else :
					nxt = ('0', 'T', 2)
			elif st[pos+1] in ['T', 'D'] :
				nxt = ('T', 2)
			else :
				nxt = ('T', 1)
		elif ch == 'V' :
			if st[pos+1] == 'V' :
				nxt = ('F', 2)
			else :
				nxt = ('F', 1)
		elif ch == 'W' :
			# can also be in middle of word
			if st[pos:pos+2] == 'WR' :
				nxt = ('R', 2)
			elif pos == first and (st[pos+1] in vowels or st[pos:pos+2] == 'WH') :
				# Wasserman should match Vasserman
				if st[pos+1] in vowels :
					nxt = ('A', 'F', 1)
				else :
					nxt = ('A', 1)
			# Arnow should match Arnoff
			elif (pos == last and st[pos-1] in vowels) \
			   or st[pos-1:pos+5] in ["EWSKI", "EWSKY", "OWSKI", "OWSKY"] \
			   or st[first:first+3] == 'SCH' :
				nxt = ('', 'F', 1)
			# polish e.g. 'filipowicz'
			elif st[pos:pos+4] in ["WICZ", "WITZ"] :
				nxt = ('TS', 'FX', 4)
			else : # default is to skip it
				nxt = (None, 1)
		elif ch == 'X' :
			# french e.g. breaux
			nxt = (None,)
			if not(pos == last and (st[pos-3:pos] in ["IAU", "EAU"] \
			   or st[pos-2:pos] in ['AU', 'OU'])):
				nxt = ('KS',)
			if st[pos+1] in ['C', 'X'] :
				nxt = nxt + (2,)
			else :
				nxt = nxt + (1,)
		elif ch == 'Z' :
			# chinese pinyin e.g. 'zhao'
			if st[pos+1] == 'H' :
				nxt = ('J',)
			elif st[pos+1:pos+3] in ["ZO", "ZI", "ZA"] \
			   or (is_slavo_germanic and pos > first and st[pos-1] != 'T') :
				nxt = ('S', 'TS')
			else :
				nxt = ('S',)
			if st[pos+1] == 'Z' :
				nxt = nxt + (2,)
			else :
				nxt = nxt + (1,)
		# ----------------------------------
		# --- end checking letters------
		# ----------------------------------
		#print str(nxt)
		if len(nxt) == 2 :
			if nxt[0] :
				pri += nxt[0]
				sec += nxt[0]
			pos += nxt[1]
		elif len(nxt) == 3 :
			if nxt[0] :
				pri += nxt[0]
			if nxt[1] :
				sec += nxt[1]
			pos += nxt[2]
	if pri == sec :
		return (pri, None)
	else :
		return (pri, sec)

if __name__ == '__main__' :
	names = {'maurice':('MRS', None),'aubrey':('APR', None),'cambrillo':('KMPRL','KMPR')\
        ,'heidi':('HT', None),'katherine':('K0RN','KTRN'),'Thumbail':('0MPL','TMPL')\
		,'catherine':('K0RN','KTRN'),'richard':('RXRT','RKRT'),'bob':('PP', None)\
        ,'eric':('ARK', None),'geoff':('JF','KF'),'Through':('0R','TR'), 'Schwein':('XN', 'XFN')\
		,'dave':('TF', None),'ray':('R', None),'steven':('STFN', None),'bryce':('PRS', None)\
        ,'randy':('RNT', None),'bryan':('PRN', None),'Rapelje':('RPL', None)\
		,'brian':('PRN', None),'otto':('AT', None),'auto':('AT', None), 'Dallas':('TLS', None)\
        , 'maisey':('MS', None), 'zhang':('JNK', None), 'Chile':('XL', None)\
        ,'Jose':('HS', None), 'Arnow':('ARN','ARNF'), 'solilijs':('SLLS', None)\
		, 'Parachute':('PRKT', None), 'Nowhere':('NR', None), 'Tux':('TKS', None)}
	for name in names.keys() :
		assert (dm(name) == names[name]), 'For "%s" function returned %s. Should be %s.' % (name, dm(name), names[name])