abydos.distance.sift4.sift4_simplest() - Code Metrics - Inspection of "Merge pull request #120 from chrislit/modularize" - chrislit/abydos - Measure and Improve Code Quality continuously with Scrutinizer

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by Chris

created 2018-10-19 22:32 UTC

abydos.distance.sift4.sift4_simplest() F

↳ Parent: abydos.distance.sift4

Complexity

Conditions

Size

Total Lines	60
Code Lines	33

Duplication

Lines	0
Ratio	0 %

Importance

Changes

Metric	Value
cc	14
eloc	33
nop	3
dl	0
loc	60
rs	3.6
c	0
b	0
f	0

How to fix Long Method Complexity

# -*- coding: utf-8 -*-

# Copyright 2018 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.sift4.

The distance.sift4 module implements Sift4 approximate string distance
functions.
"""

from __future__ import division, unicode_literals

from six.moves import range


__all__ = ['dist_sift4', 'sift4_common', 'sift4_simplest', 'sim_sift4']


def sift4_simplest(src, tar, max_offset=5):
    """Return the "simplest" Sift4 distance between two terms.

    This is an approximation of edit distance, described in
    :cite:`Zackwehdex:2014`.

    :param str src: source string for comparison
    :param str tar: target string for comparison
    :param max_offset: the number of characters to search for matching letters
    :returns: the Sift4 distance according to the simplest formula
    :rtype: int

    >>> sift4_simplest('cat', 'hat')
    1
    >>> sift4_simplest('Niall', 'Neil')
    2
    >>> sift4_simplest('Colin', 'Cuilen')
    3
    >>> sift4_simplest('ATCG', 'TAGC')
    2
    """
    if not src:
        return len(tar)

    if not tar:
        return len(src)

    src_len = len(src)
    tar_len = len(tar)

    src_cur = 0
    tar_cur = 0
    lcss = 0
    local_cs = 0

    while (src_cur < src_len) and (tar_cur < tar_len):
        if src[src_cur] == tar[tar_cur]:
            local_cs += 1
        else:
            lcss += local_cs
            local_cs = 0
            if src_cur != tar_cur:
                src_cur = tar_cur = max(src_cur, tar_cur)
            for i in range(max_offset):
                if not ((src_cur+i < src_len) or (tar_cur+i < tar_len)):
                    break
                if (src_cur+i < src_len) and (src[src_cur+i] == tar[tar_cur]):
                    src_cur += i
                    local_cs += 1
                    break
                if (tar_cur+i < tar_len) and (src[src_cur] == tar[tar_cur+i]):
                    tar_cur += i
                    local_cs += 1
                    break

        src_cur += 1
        tar_cur += 1

    lcss += local_cs
    return round(max(src_len, tar_len) - lcss)


def sift4_common(src, tar, max_offset=5, max_distance=0):
    """Return the "common" Sift4 distance between two terms.

    This is an approximation of edit distance, described in
    :cite:`Zackwehdex:2014`.

    :param str src: source string for comparison
    :param str tar: target string for comparison
    :param max_offset: the number of characters to search for matching letters
    :param max_distance: the distance at which to stop and exit
    :returns: the Sift4 distance according to the common formula
    :rtype: int

    >>> sift4_common('cat', 'hat')
    1
    >>> sift4_common('Niall', 'Neil')
    2
    >>> sift4_common('Colin', 'Cuilen')
    3
    >>> sift4_common('ATCG', 'TAGC')
    2
    """
    if not src:
        return len(tar)

    if not tar:
        return len(src)

    src_len = len(src)
    tar_len = len(tar)

    src_cur = 0
    tar_cur = 0
    lcss = 0
    local_cs = 0
    trans = 0
    offset_arr = []

    while (src_cur < src_len) and (tar_cur < tar_len):
        if src[src_cur] == tar[tar_cur]:
            local_cs += 1
            is_trans = False
            i = 0
            while i < len(offset_arr):
                ofs = offset_arr[i]
                if src_cur <= ofs['src_cur'] or tar_cur <= ofs['tar_cur']:
                    is_trans = (abs(tar_cur-src_cur) >=
                                abs(ofs['tar_cur']-ofs['src_cur']))
                    if is_trans:
                        trans += 1
                    elif not ofs['trans']:
                        ofs['trans'] = True
                        trans += 1
                    break
                elif src_cur > ofs['tar_cur'] and tar_cur > ofs['src_cur']:
                    del offset_arr[i]
                else:
                    i += 1

            offset_arr.append({'src_cur': src_cur, 'tar_cur': tar_cur,
                               'trans': is_trans})
        else:
            lcss += local_cs
            local_cs = 0
            if src_cur != tar_cur:
                src_cur = tar_cur = min(src_cur, tar_cur)
            for i in range(max_offset):
                if not ((src_cur+i < src_len) or (tar_cur+i < tar_len)):
                    break
                if (src_cur+i < src_len) and (src[src_cur+i] == tar[tar_cur]):
                    src_cur += i-1
                    tar_cur -= 1
                    break
                if (tar_cur+i < tar_len) and (src[src_cur] == tar[tar_cur+i]):
                    src_cur -= 1
                    tar_cur += i-1
                    break

        src_cur += 1
        tar_cur += 1

        if max_distance:
            temporary_distance = max(src_cur, tar_cur) - lcss + trans
            if temporary_distance >= max_distance:
                return round(temporary_distance)

        if (src_cur >= src_len) or (tar_cur >= tar_len):
            lcss += local_cs
            local_cs = 0
            src_cur = tar_cur = min(src_cur, tar_cur)

    lcss += local_cs
    return round(max(src_len, tar_len) - lcss + trans)


def dist_sift4(src, tar, max_offset=5, max_distance=0):
    """Return the normalized "common" Sift4 distance between two terms.

    This is Sift4 distance, normalized to [0, 1].

    :param str src: source string for comparison
    :param str tar: target string for comparison
    :param max_offset: the number of characters to search for matching letters
    :param max_distance: the distance at which to stop and exit
    :returns: the normalized Sift4 distance
    :rtype: float

    >>> round(dist_sift4('cat', 'hat'), 12)
    0.333333333333
    >>> dist_sift4('Niall', 'Neil')
    0.4
    >>> dist_sift4('Colin', 'Cuilen')
    0.5
    >>> dist_sift4('ATCG', 'TAGC')
    0.5
    """
    return (sift4_common(src, tar, max_offset, max_distance) /
            (max(len(src), len(tar), 1)))


def sim_sift4(src, tar, max_offset=5, max_distance=0):
    """Return the normalized "common" Sift4 similarity of two terms.

    Normalized Sift4 similarity is the complement of normalized Sift4 distance:
    :math:`sim_{Sift4} = 1 - dist_{Sift4}`.

    :param str src: source string for comparison
    :param str tar: target string for comparison
    :param max_offset: the number of characters to search for matching letters
    :param max_distance: the distance at which to stop and exit
    :returns: the normalized Sift4 similarity
    :rtype: float

    >>> round(sim_sift4('cat', 'hat'), 12)
    0.666666666667
    >>> sim_sift4('Niall', 'Neil')
    0.6
    >>> sim_sift4('Colin', 'Cuilen')
    0.5
    >>> sim_sift4('ATCG', 'TAGC')
    0.5
    """
    return 1-dist_sift4(src, tar, max_offset, max_distance)


if __name__ == '__main__':
    import doctest
    doctest.testmod()


1			# -- coding: utf-8 --
2
3			# Copyright 2018 by Christopher C. Little.
4			# This file is part of Abydos.
5			#
6			# Abydos is free software: you can redistribute it and/or modify
7			# it under the terms of the GNU General Public License as published by
8			# the Free Software Foundation, either version 3 of the License, or
9			# (at your option) any later version.
10			#
11			# Abydos is distributed in the hope that it will be useful,
12			# but WITHOUT ANY WARRANTY; without even the implied warranty of
13			# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14			# GNU General Public License for more details.
15			#
16			# You should have received a copy of the GNU General Public License
17			# along with Abydos. If not, see <http://www.gnu.org/licenses/>.
18
19			"""abydos.distance.sift4.
20
21			The distance.sift4 module implements Sift4 approximate string distance
22			functions.
23			"""
24
25			from __future__ import division, unicode_literals
26
27			from six.moves import range
28
29
30			__all__ = ['dist_sift4', 'sift4_common', 'sift4_simplest', 'sim_sift4']
31
32
33			def sift4_simplest(src, tar, max_offset=5):
34			"""Return the "simplest" Sift4 distance between two terms.
35
36			This is an approximation of edit distance, described in
37			:cite:`Zackwehdex:2014`.
38
39			:param str src: source string for comparison
40			:param str tar: target string for comparison
41			:param max_offset: the number of characters to search for matching letters
42			:returns: the Sift4 distance according to the simplest formula
43			:rtype: int
44
45			>>> sift4_simplest('cat', 'hat')
46			1
47			>>> sift4_simplest('Niall', 'Neil')
48			2
49			>>> sift4_simplest('Colin', 'Cuilen')
50			3
51			>>> sift4_simplest('ATCG', 'TAGC')
52			2
53			"""
54			if not src:
55			return len(tar)
56
57			if not tar:
58			return len(src)
59
60			src_len = len(src)
61			tar_len = len(tar)
62
63			src_cur = 0
64			tar_cur = 0
65			lcss = 0
66			local_cs = 0
67
68			while (src_cur < src_len) and (tar_cur < tar_len):
69			if src[src_cur] == tar[tar_cur]:
70			local_cs += 1
71			else:
72			lcss += local_cs
73			local_cs = 0
74			if src_cur != tar_cur:
75			src_cur = tar_cur = max(src_cur, tar_cur)
76			for i in range(max_offset):
77			if not ((src_cur+i < src_len) or (tar_cur+i < tar_len)):
78			break
79			if (src_cur+i < src_len) and (src[src_cur+i] == tar[tar_cur]):
80			src_cur += i
81			local_cs += 1
82			break
83			if (tar_cur+i < tar_len) and (src[src_cur] == tar[tar_cur+i]):
84			tar_cur += i
85			local_cs += 1
86			break
87
88			src_cur += 1
89			tar_cur += 1
90
91			lcss += local_cs
92			return round(max(src_len, tar_len) - lcss)
93
94
95			def sift4_common(src, tar, max_offset=5, max_distance=0):
96			"""Return the "common" Sift4 distance between two terms.
97
98			This is an approximation of edit distance, described in
99			:cite:`Zackwehdex:2014`.
100
101			:param str src: source string for comparison
102			:param str tar: target string for comparison
103			:param max_offset: the number of characters to search for matching letters
104			:param max_distance: the distance at which to stop and exit
105			:returns: the Sift4 distance according to the common formula
106			:rtype: int
107
108			>>> sift4_common('cat', 'hat')
109			1
110			>>> sift4_common('Niall', 'Neil')
111			2
112			>>> sift4_common('Colin', 'Cuilen')
113			3
114			>>> sift4_common('ATCG', 'TAGC')
115			2
116			"""
117			if not src:
118			return len(tar)
119
120			if not tar:
121			return len(src)
122
123			src_len = len(src)
124			tar_len = len(tar)
125
126			src_cur = 0
127			tar_cur = 0
128			lcss = 0
129			local_cs = 0
130			trans = 0
131			offset_arr = []
132
133			while (src_cur < src_len) and (tar_cur < tar_len):
134			if src[src_cur] == tar[tar_cur]:
135			local_cs += 1
136			is_trans = False
137			i = 0
138			while i < len(offset_arr):
139			ofs = offset_arr[i]
140			if src_cur <= ofs['src_cur'] or tar_cur <= ofs['tar_cur']:
141			is_trans = (abs(tar_cur-src_cur) >=
142			abs(ofs['tar_cur']-ofs['src_cur']))
143			if is_trans:
144			trans += 1
145			elif not ofs['trans']:
146			ofs['trans'] = True
147			trans += 1
148			break
149			elif src_cur > ofs['tar_cur'] and tar_cur > ofs['src_cur']:
150			del offset_arr[i]
151			else:
152			i += 1
153
154			offset_arr.append({'src_cur': src_cur, 'tar_cur': tar_cur,
155			'trans': is_trans})
156			else:
157			lcss += local_cs
158			local_cs = 0
159			if src_cur != tar_cur:
160			src_cur = tar_cur = min(src_cur, tar_cur)
161			for i in range(max_offset):
162			if not ((src_cur+i < src_len) or (tar_cur+i < tar_len)):
163			break
164			if (src_cur+i < src_len) and (src[src_cur+i] == tar[tar_cur]):
165			src_cur += i-1
166			tar_cur -= 1
167			break
168			if (tar_cur+i < tar_len) and (src[src_cur] == tar[tar_cur+i]):
169			src_cur -= 1
170			tar_cur += i-1
171			break
172
173			src_cur += 1
174			tar_cur += 1
175
176			if max_distance:
177			temporary_distance = max(src_cur, tar_cur) - lcss + trans
178			if temporary_distance >= max_distance:
179			return round(temporary_distance)
180
181			if (src_cur >= src_len) or (tar_cur >= tar_len):
182			lcss += local_cs
183			local_cs = 0
184			src_cur = tar_cur = min(src_cur, tar_cur)
185
186			lcss += local_cs
187			return round(max(src_len, tar_len) - lcss + trans)
188
189
190			def dist_sift4(src, tar, max_offset=5, max_distance=0):
191			"""Return the normalized "common" Sift4 distance between two terms.
192
193			This is Sift4 distance, normalized to [0, 1].
194
195			:param str src: source string for comparison
196			:param str tar: target string for comparison
197			:param max_offset: the number of characters to search for matching letters
198			:param max_distance: the distance at which to stop and exit
199			:returns: the normalized Sift4 distance
200			:rtype: float
201
202			>>> round(dist_sift4('cat', 'hat'), 12)
203			0.333333333333
204			>>> dist_sift4('Niall', 'Neil')
205			0.4
206			>>> dist_sift4('Colin', 'Cuilen')
207			0.5
208			>>> dist_sift4('ATCG', 'TAGC')
209			0.5
210			"""
211			return (sift4_common(src, tar, max_offset, max_distance) /
212			(max(len(src), len(tar), 1)))
213
214
215			def sim_sift4(src, tar, max_offset=5, max_distance=0):
216			"""Return the normalized "common" Sift4 similarity of two terms.
217
218			Normalized Sift4 similarity is the complement of normalized Sift4 distance:
219			:math:`sim_{Sift4} = 1 - dist_{Sift4}`.
220
221			:param str src: source string for comparison
222			:param str tar: target string for comparison
223			:param max_offset: the number of characters to search for matching letters
224			:param max_distance: the distance at which to stop and exit
225			:returns: the normalized Sift4 similarity
226			:rtype: float
227
228			>>> round(sim_sift4('cat', 'hat'), 12)
229			0.666666666667
230			>>> sim_sift4('Niall', 'Neil')
231			0.6
232			>>> sim_sift4('Colin', 'Cuilen')
233			0.5
234			>>> sim_sift4('ATCG', 'TAGC')
235			0.5
236			"""
237			return 1-dist_sift4(src, tar, max_offset, max_distance)
238
239
240			if __name__ == '__main__':
241			import doctest
242			doctest.testmod()
243

chrislit / abydos

Push — master ( 64abe2...a464fa )

abydos.distance.sift4.sift4_simplest() F

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