abydos.phonetic.metaphone.metaphone()

Complexity

Conditions

80

Size

Total Lines	167
Code Lines	109

Duplication

Lines	0
Ratio	0 %

Importance

Changes

0

# -*- coding: utf-8 -*-
def metaphone(word, max_length=-1):
    """Return the Metaphone code for a word.

    Based on Lawrence Philips' Pick BASIC code from 1990 :cite:`Philips:1990`,
    as described in :cite:`Philips:1990b`.
    This incorporates some corrections to the above code, particularly
    some of those suggested by Michael Kuhn in :cite:`Kuhn:1995`.

    :param str word: the word to transform
    :param int max_length: the maximum length of the returned Metaphone code
        (defaults to 64, but in Philips' original implementation this was 4)
    :returns: the Metaphone value
    :rtype: str


    >>> metaphone('Christopher')
    'KRSTFR'
    >>> metaphone('Niall')
    'NL'
    >>> metaphone('Smith')
    'SM0'
    >>> metaphone('Schmidt')
    'SKMTT'
    """
    _vowels = {'A', 'E', 'I', 'O', 'U'}
    _frontv = {'E', 'I', 'Y'}
    _varson = {'C', 'G', 'P', 'S', 'T'}

    # Require a max_length of at least 4
    if max_length != -1:
        max_length = max(4, max_length)
    else:
        max_length = 64

    # As in variable sound--those modified by adding an "h"
    ename = ''.join(c for c in word.upper() if c.isalnum())
    ename = ename.replace('ß', 'SS')

    # Delete non-alphanumeric characters and make all caps
    if not ename:
        return ''
    if ename[0:2] in {'PN', 'AE', 'KN', 'GN', 'WR'}:
        ename = ename[1:]
    elif ename[0] == 'X':
        ename = 'S' + ename[1:]
    elif ename[0:2] == 'WH':
        ename = 'W' + ename[2:]

    # Convert to metaphone
    elen = len(ename)-1
    metaph = ''
    for i in range(len(ename)):
        if len(metaph) >= max_length:
            break
        if ((ename[i] not in {'G', 'T'} and
             i > 0 and ename[i-1] == ename[i])):
            continue

        if ename[i] in _vowels and i == 0:
            metaph = ename[i]

        elif ename[i] == 'B':
            if i != elen or ename[i-1] != 'M':
                metaph += ename[i]

        elif ename[i] == 'C':
            if not (i > 0 and ename[i-1] == 'S' and ename[i+1:i+2] in _frontv):
                if ename[i+1:i+3] == 'IA':
                    metaph += 'X'
                elif ename[i+1:i+2] in _frontv:
                    metaph += 'S'
                elif i > 0 and ename[i-1:i+2] == 'SCH':
                    metaph += 'K'
                elif ename[i+1:i+2] == 'H':
                    if i == 0 and i+1 < elen and ename[i+2:i+3] not in _vowels:
                        metaph += 'K'
                    else:
                        metaph += 'X'
                else:
                    metaph += 'K'

        elif ename[i] == 'D':
            if ename[i+1:i+2] == 'G' and ename[i+2:i+3] in _frontv:
                metaph += 'J'
            else:
                metaph += 'T'

        elif ename[i] == 'G':
            if ename[i+1:i+2] == 'H' and not (i+1 == elen or
                                              ename[i+2:i+3] not in _vowels):
                continue
            elif i > 0 and ((i+1 == elen and ename[i+1] == 'N') or
                            (i+3 == elen and ename[i+1:i+4] == 'NED')):
                continue
            elif (i-1 > 0 and i+1 <= elen and ename[i-1] == 'D' and
                  ename[i+1] in _frontv):
                continue
            elif ename[i+1:i+2] == 'G':
                continue
            elif ename[i+1:i+2] in _frontv:
                if i == 0 or ename[i-1] != 'G':
                    metaph += 'J'
                else:
                    metaph += 'K'
            else:
                metaph += 'K'

        elif ename[i] == 'H':
            if ((i > 0 and ename[i-1] in _vowels and
                 ename[i+1:i+2] not in _vowels)):
                continue
            elif i > 0 and ename[i-1] in _varson:
                continue
            else:
                metaph += 'H'

        elif ename[i] in {'F', 'J', 'L', 'M', 'N', 'R'}:
            metaph += ename[i]

        elif ename[i] == 'K':
            if i > 0 and ename[i-1] == 'C':
                continue
            else:
                metaph += 'K'

        elif ename[i] == 'P':
            if ename[i+1:i+2] == 'H':
                metaph += 'F'
            else:
                metaph += 'P'

        elif ename[i] == 'Q':
            metaph += 'K'

        elif ename[i] == 'S':
            if ((i > 0 and i+2 <= elen and ename[i+1] == 'I' and
                 ename[i+2] in 'OA')):
                metaph += 'X'
            elif ename[i+1:i+2] == 'H':
                metaph += 'X'
            else:
                metaph += 'S'

        elif ename[i] == 'T':
            if ((i > 0 and i+2 <= elen and ename[i+1] == 'I' and
                 ename[i+2] in {'A', 'O'})):
                metaph += 'X'
            elif ename[i+1:i+2] == 'H':
                metaph += '0'
            elif ename[i+1:i+3] != 'CH':
                if ename[i-1:i] != 'T':
                    metaph += 'T'

        elif ename[i] == 'V':
            metaph += 'F'

        elif ename[i] in 'WY':
            if ename[i+1:i+2] in _vowels:
                metaph += ename[i]

        elif ename[i] == 'X':
            metaph += 'KS'

        elif ename[i] == 'Z':
            metaph += 'S'

    return metaph