Source code for pm4py.util.string_distance

import sys
import importlib.util
from typing import List, Union




def levenshtein_distance(s1, s2):
    if len(s1) < len(s2):
        return levenshtein_distance(s2, s1)

    if len(s2) == 0:
        return len(s1)

    previous_row = range(len(s2) + 1)
    for i, c1 in enumerate(s1):
        current_row = [i + 1]
        for j, c2 in enumerate(s2):
            insertions = previous_row[j + 1] + 1
            deletions = current_row[j] + 1
            substitutions = previous_row[j] + (c1 != c2)
            current_row.append(min(insertions, deletions, substitutions))
        previous_row = current_row

    return previous_row[-1]





def levenshtein(stru1, stru2):
    if importlib.util.find_spec("stringdist"):
        import stringdist

        return stringdist.levenshtein(stru1, stru2)

    return levenshtein_distance(stru1, stru2)





def argmin_levenshtein(stru: str, list_stri: List[str]) -> Union[str, None]:
    """
    Given a string (stru), finds a string in a list
    of strings (list_stri) that minimizes the Levenshtein distance.

    Parameters
    --------------
    stru
         String (that is compared)
    list_stri
        List of comparison strings

    Returns
    --------------
    argmin_dist
        String (belonging to list_stri) that minimizes the Levenshtein distance
        with the 'stru' argument
    """
    if list_stri:
        len_stru = len(stru)
        argmin_dist = None
        min_edit_dist = sys.maxsize
        # sort the strings in the list based on the actual length in comparison
        # to the provided string
        list_stri = sorted(list_stri, key=lambda x: abs(len(x) - len_stru))
        for comp_stri in list_stri:
            this_length_diff = abs(len(comp_stri) - len_stru)
            # to make things faster, breaks whether we reach a string
            # which distance is greater or equal than the edit distance
            # with a previous string, because the edit distance would then
            # be trivially greater or equal in length
            if this_length_diff >= min_edit_dist:
                break
            dist_this_comp = levenshtein(stru, comp_stri)
            if dist_this_comp < min_edit_dist:
                argmin_dist = comp_stri
                min_edit_dist = dist_this_comp
        return argmin_dist
    return None





def argmax_levenshtein(stru: str, list_stri: List[str]) -> Union[str, None]:
    """
    Given a string (stru), finds a string in a list
    of strings (list_stri) that maximizes the Levenshtein distance.

    Parameters
    --------------
    stru
         String (that is compared)
    list_stri
        List of comparison strings

    Returns
    --------------
    argmax_dist
        String (belonging to list_stri) that maximizes the Levenshtein distance
        with the 'stru' argument
    """
    if list_stri:
        len_stru = len(stru)
        argmax_dist = None
        max_edit_dist = 0
        # sort the strings in the list based on the actual length in comparison
        # to the provided string
        list_stri = sorted(list_stri, key=lambda x: -len(x))
        for comp_stri in list_stri:
            # to make things faster, breaks whether the
            # following condition is reached
            if len(comp_stri) + len_stru <= max_edit_dist:
                break
            dist_this_comp = levenshtein(stru, comp_stri)
            if dist_this_comp > max_edit_dist:
                argmax_dist = comp_stri
                max_edit_dist = dist_this_comp
        return argmax_dist
    return None