abydos/fingerprint/_lc_cutter.py
# Copyright 2019-2020 by Christopher C. Little.
# This file is part of Abydos.
#
# Abydos is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# Abydos is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Abydos. If not, see <http://www.gnu.org/licenses/>.
"""abydos.fingerprint._lc_cutter.
Library of Congress Cutter table encoding
"""
from ._fingerprint import _Fingerprint
__all__ = ['LCCutter']
class LCCutter(_Fingerprint):
"""Library of Congress Cutter table encoding.
This is based on the Library of Congress Cutter table encoding scheme, as
described at https://www.loc.gov/aba/pcc/053/table.html :cite:`LOC:2013`.
Handling for numerals is not included.
.. versionadded:: 0.4.1
"""
_vowels = set('AEIOU')
_after_initial_vowel = ['C', 'K', 'M', 'O', 'Q', 'R', 'T']
_after_initial_s = ['C', 'D', 'G', 'L', 'S', 'T', 'U']
_after_initial_qu = ['D', 'H', 'N', 'Q', 'S', 'X']
_after_initial_cons = ['D', 'H', 'N', 'Q', 'T', 'X']
_expansions = ['D', 'H', 'L', 'O', 'S', 'V']
def __init__(self, max_length: int = 64) -> None:
"""Initialize LCCutter instance.
Parameters
----------
max_length : int
The length of the code returned (defaults to 64)
.. versionadded:: 0.4.1
"""
super(LCCutter, self).__init__()
# Require a max_length of at least 2 and not more than 64
if max_length != -1:
self._max_length = min(max(2, max_length), 64)
else:
self._max_length = 64
def fingerprint(self, word: str) -> str:
"""Return the Library of Congress Cutter table encoding of a word.
Parameters
----------
word : str
The word to fingerprint
Returns
-------
str
The Library of Congress Cutter table encoding
Examples
--------
>>> cf = LCCutter()
>>> cf.fingerprint('hat')
'H38'
>>> cf.fingerprint('niall')
'N5355'
>>> cf.fingerprint('colin')
'C6556'
>>> cf.fingerprint('atcg')
'A834'
>>> cf.fingerprint('entreatment')
'E5874386468'
.. versionadded:: 0.4.1
"""
# uppercase
uc = ''.join(letter for letter in word.upper() if letter.isalpha())
if not uc:
return ''
code = uc[0]
# length 1
if len(uc) == 1:
return code
# length 2+
code_list = [code]
# first cutter
pos = 1
if uc[0] in self._vowels:
cval = 2
for letter in self._after_initial_vowel:
if uc[1] > letter:
cval += 1
else:
break
elif uc[0] == 'S':
cval = 2
for letter in self._after_initial_s:
if uc[1] > letter:
cval += 1
elif uc[1] == 'C' and uc[1:3] < 'CI':
cval += 1
pos += 1
break
else:
break
elif uc[0:2] == 'QU':
cval = 3
pos += 1
for letter in self._after_initial_qu:
if uc[2:3] > letter:
cval += 1
else:
break
elif 'QA' <= uc[0:2] <= 'QT':
cval = 2
else:
cval = 3
for letter in self._after_initial_cons:
if uc[1] > letter:
cval += 1
else:
break
code_list.append(str(cval))
# length 3+
for ch in uc[pos + 1 :]:
if len(code_list) >= self._max_length:
break
cval = 3
for letter in self._expansions:
if ch > letter:
cval += 1
else:
break
code_list.append(str(cval))
return ''.join(code_list[: self._max_length])
if __name__ == '__main__':
import doctest
doctest.testmod()