# Copyright 2014-2020 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.distance._indel.
Indel distance
"""
from typing import Any
from ._levenshtein import Levenshtein
__all__ = ['Indel']
[docs]
class Indel(Levenshtein):
"""Indel distance.
This is equivalent to Levenshtein distance, when only inserts and deletes
are possible.
.. versionadded:: 0.3.6
"""
def __init__(self, **kwargs: Any) -> None:
"""Initialize Levenshtein instance.
Parameters
----------
**kwargs
Arbitrary keyword arguments
.. versionadded:: 0.4.0
"""
super(Indel, self).__init__(
mode='lev', cost=(1, 1, float('inf'), float('inf')), **kwargs
)
[docs]
def dist(self, src: str, tar: str) -> float:
"""Return the normalized indel distance between two strings.
This is equivalent to normalized Levenshtein distance, when only
inserts and deletes are possible.
Parameters
----------
src : str
Source string for comparison
tar : str
Target string for comparison
Returns
-------
float
Normalized indel distance
Examples
--------
>>> cmp = Indel()
>>> round(cmp.dist('cat', 'hat'), 12)
0.333333333333
>>> round(cmp.dist('Niall', 'Neil'), 12)
0.333333333333
>>> round(cmp.dist('Colin', 'Cuilen'), 12)
0.454545454545
>>> cmp.dist('ATCG', 'TAGC')
0.5
.. versionadded:: 0.3.6
"""
if src == tar:
return 0.0
return self.dist_abs(src, tar) / (len(src) + len(tar))
if __name__ == '__main__':
import doctest
doctest.testmod()