# Copyright 2018-2020 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._position.
Cisłak & Grabowski's position fingerprint
"""
from typing import Dict, Tuple
from ._fingerprint import MOST_COMMON_LETTERS_CG, _Fingerprint
__all__ = ['Position']
[docs]
class Position(_Fingerprint):
"""Position Fingerprint.
Based on the position fingerprint from :cite:`Cislak:2017`.
.. versionadded:: 0.3.6
"""
def __init__(
self,
n_bits: int = 16,
most_common: Tuple[str, ...] = MOST_COMMON_LETTERS_CG,
bits_per_letter: int = 3,
) -> None:
"""Initialize Count instance.
Parameters
----------
n_bits : int
Number of bits in the fingerprint returned
most_common : list
The most common tokens in the target language, ordered by frequency
.. versionadded:: 0.4.0
"""
super(Position, self).__init__()
self._n_bits = n_bits
self._most_common = most_common
self._bits_per_letter = bits_per_letter
[docs]
def fingerprint(self, word: str) -> str:
"""Return the position fingerprint.
Parameters
----------
word : str
The word to fingerprint
Returns
-------
str
The position fingerprint
Examples
--------
>>> pf = Position()
>>> pf.fingerprint('hat')
'1110100011111111'
>>> pf.fingerprint('niall')
'1111110101110010'
>>> pf.fingerprint('colin')
'1111111110010111'
>>> pf.fingerprint('atcg')
'1110010001111111'
>>> pf.fingerprint('entreatment')
'0000101011111111'
.. versionadded:: 0.3.0
.. versionchanged:: 0.3.6
Encapsulated in class
.. versionchanged:: 0.6.0
Changed to return a str and added fingerprint_int method
"""
return ('{:0' + str(self._n_bits) + 'b}').format(
self.fingerprint_int(word)
)
[docs]
def fingerprint_int(self, word: str) -> int:
"""Return the position fingerprint.
Parameters
----------
word : str
The word to fingerprint
Returns
-------
int
The position fingerprint as an int
Examples
--------
>>> pf = Position()
>>> pf.fingerprint_int('hat')
59647
>>> pf.fingerprint_int('niall')
64882
>>> pf.fingerprint_int('colin')
65431
>>> pf.fingerprint_int('atcg')
58495
>>> pf.fingerprint_int('entreatment')
2815
.. versionadded:: 0.6.0
"""
n_bits = self._n_bits
position = {} # type: Dict[str, int]
for pos, letter in enumerate(word):
if letter not in position and letter in self._most_common:
position[letter] = min(pos, 2 ** self._bits_per_letter - 1)
fingerprint = 0
for letter in self._most_common:
if n_bits:
fingerprint <<= min(self._bits_per_letter, n_bits)
if letter in position:
fingerprint += min(position[letter], 2 ** n_bits - 1)
else:
fingerprint += min(
2 ** self._bits_per_letter - 1, 2 ** n_bits - 1
)
n_bits -= min(self._bits_per_letter, n_bits)
else:
break
for _ in range(n_bits):
fingerprint <<= 1
fingerprint += 1
return fingerprint
if __name__ == '__main__':
import doctest
doctest.testmod()