python-string-similarity/strsimpy/qgram.py

# Copyright (c) 2018 luozhouyang
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.

from .shingle_based import ShingleBased
from .string_distance import StringDistance


class QGram(ShingleBased, StringDistance):

    def __init__(self, k=3):
        super().__init__(k)

    def distance(self, s0, s1):
        if s0 is None:
            raise TypeError("Argument s0 is NoneType.")
        if s1 is None:
            raise TypeError("Argument s1 is NoneType.")
        if s0 == s1:
            return 0.0

        profile0 = self.get_profile(s0)
        profile1 = self.get_profile(s1)
        return self.distance_profile(profile0, profile1)

    @staticmethod
    def distance_profile(profile0, profile1):
        union = set()
        for k in profile0.keys():
            union.add(k)
        for k in profile1.keys():
            union.add(k)
        agg = 0
        for k in union:
            v0, v1 = 0, 0
            if profile0.get(k) is not None:
                v0 = int(profile0.get(k))
            if profile1.get(k) is not None:
                v1 = int(profile1.get(k))
            agg += abs(v0 - v1)
        return agg