# 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.distance._lcprefix.
Longest common prefix
"""
from os.path import commonprefix
from ._distance import _Distance
__all__ = ['LCPrefix']
[docs]class LCPrefix(_Distance):
"""Longest common prefix.
.. versionadded:: 0.4.0
"""
[docs] def lcprefix(self, strings):
"""Return the longest common prefix of a list of strings.
Longest common prefix (LCPrefix).
Parameters
----------
strings : list of strings
Strings for comparison
Returns
-------
str
The longest common prefix
Examples
--------
>>> pfx = LCPrefix()
>>> pfx.lcprefix(['cat', 'hat'])
''
>>> pfx.lcprefix(['Niall', 'Neil'])
'N'
>>> pfx.lcprefix(['aluminum', 'Catalan'])
''
>>> pfx.lcprefix(['ATCG', 'TAGC'])
''
.. versionadded:: 0.4.0
"""
return commonprefix(strings)
[docs] def dist_abs(self, src, tar, *args):
"""Return the length of the longest common prefix of the strings.
Parameters
----------
src : str
Source string for comparison
tar : str
Target string for comparison
*args : strs
Additional strings for comparison
Raises
------
ValueError
All arguments must be of type str
Returns
-------
int
The length of the longest common prefix
Examples
--------
>>> pfx = LCPrefix()
>>> pfx.dist_abs('cat', 'hat')
0
>>> pfx.dist_abs('Niall', 'Neil')
1
>>> pfx.dist_abs('aluminum', 'Catalan')
0
>>> pfx.dist_abs('ATCG', 'TAGC')
0
.. versionadded:: 0.4.0
"""
strings = [src, tar]
for arg in args:
if isinstance(arg, str):
strings.append(arg)
else:
raise TypeError('All arguments must be of type str')
return len(self.lcprefix(strings))
[docs] def sim(self, src, tar, *args):
r"""Return the longest common prefix similarity of two or more strings.
Longest common prefix similarity (:math:`sim_{LCPrefix}`).
This employs the LCPrefix function to derive a similarity metric:
:math:`sim_{LCPrefix}(s,t) = \frac{|LCPrefix(s,t)|}{max(|s|, |t|)}`
Parameters
----------
src : str
Source string for comparison
tar : str
Target string for comparison
*args : strs
Additional strings for comparison
Returns
-------
float
LCPrefix similarity
Examples
--------
>>> pfx = LCPrefix()
>>> pfx.sim('cat', 'hat')
0.0
>>> pfx.sim('Niall', 'Neil')
0.2
>>> pfx.sim('aluminum', 'Catalan')
0.0
>>> pfx.sim('ATCG', 'TAGC')
0.0
.. versionadded:: 0.4.0
"""
if src == tar:
return 1.0
elif not src or not tar:
return 0.0
dist = self.dist_abs(src, tar, *args)
maxlen = max(len(src), len(tar), *[len(arg) for arg in args])
return dist / maxlen
if __name__ == '__main__':
import doctest
doctest.testmod()