92 lines
3.7 KiB
Python
92 lines
3.7 KiB
Python
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"""A library for finding approximate subsequence matches.
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Contains several implementations of fuzzy sub-sequence search functions. Such
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functions find parts of a sequence which match a given sub-sequence up to a
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given maximum Levenshtein distance.
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The simplest use is via the find_near_matches utility function, which chooses
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a suitable fuzzy search implementation based on the given parameters.
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Example:
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>>> find_near_matches('PATTERN', 'aaaPATERNaaa', max_l_dist=1)
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[Match(start=3, end=9, dist=1)]
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"""
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__author__ = 'Tal Einat'
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__email__ = 'taleinat@gmail.com'
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__version__ = '0.6.2'
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__all__ = [
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'find_near_matches',
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'Match',
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]
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from fuzzysearch.common import Match, search_exact, LevenshteinSearchParams
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from fuzzysearch.levenshtein import find_near_matches_levenshtein
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from fuzzysearch.substitutions_only import find_near_matches_substitutions
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from fuzzysearch.generic_search import find_near_matches_generic
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def find_near_matches(subsequence, sequence,
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max_substitutions=None,
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max_insertions=None,
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max_deletions=None,
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max_l_dist=None):
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"""search for near-matches of subsequence in sequence
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This searches for near-matches, where the nearly-matching parts of the
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sequence must meet the following limitations (relative to the subsequence):
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* the maximum allowed number of character substitutions
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* the maximum allowed number of new characters inserted
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* and the maximum allowed number of character deletions
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* the total number of substitutions, insertions and deletions
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(a.k.a. the Levenshtein distance)
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"""
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search_params = LevenshteinSearchParams(max_substitutions,
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max_insertions,
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max_deletions,
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max_l_dist)
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search_func = choose_search_func(search_params)
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return search_func(subsequence, sequence, search_params)
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def choose_search_func(search_params):
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max_substitutions, max_insertions, max_deletions, max_l_dist = search_params.unpacked
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# if the limitations are so strict that only exact matches are allowed,
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# use search_exact()
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if search_params.max_l_dist == 0:
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return lambda subsequence, sequence, search_params: [
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Match(index, index + len(subsequence), 0)
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for index in search_exact(subsequence, sequence)
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]
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# return [
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# Match(start_index, start_index + len(subsequence), 0)
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# for start_index in search_exact(subsequence, sequence)
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# ]
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# if only substitutions are allowed, use find_near_matches_substitutions()
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elif max_insertions == 0 and max_deletions == 0:
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# max_subs = \
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# min([x for x in [max_l_dist, max_substitutions] if x is not None])
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return lambda subsequence, sequence, search_params:\
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find_near_matches_substitutions(
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subsequence, sequence,
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min([x for x in [search_params.max_l_dist, search_params.max_substitutions] if x is not None])
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)
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# if it is enough to just take into account the maximum Levenshtein
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# distance, use find_near_matches_levenshtein()
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elif max_l_dist <= min(
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(max_substitutions if max_substitutions is not None else (1 << 29)),
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(max_insertions if max_insertions is not None else (1 << 29)),
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(max_deletions if max_deletions is not None else (1 << 29)),
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):
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return lambda subsequence, sequence, search_params:\
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find_near_matches_levenshtein(subsequence, sequence, search_params.max_l_dist)
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# if none of the special cases above are met, use the most generic version
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else:
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return find_near_matches_generic
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