Development - Advanced, exercise 6

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The BiGramsJaccardDistance is a technique that calculates the difference between two strings by checking how many bigrams the two strings have in common overall. A bigram is defined as a sequence of two consecutive characters – e.g. the string "john" can be split in three bigrams: "jo", "oh" and "hn". Once created two collections of bigrams (one for each string), each of which cannot contain the same bigram twice or more times, the Jaccard distance is calculated by dividing the size of the intersection of these collections with the size of the union of the same collections.

Write the Python function def bigrams_jaccard(string_1, string_2) which implements the BiGramsJaccardDistance technique and returns the number defining the distance between the strings.

Solution

# Test case for the function
def test_bigrams_jaccard(string_1, string_2, expected):
    result = bigrams_jaccard(string_1, string_2)
    if expected == result:
        return True
    else:
        return False


# Code of the function
def bigrams_jaccard(string_1, string_2):
    bigrams_s1 = get_bigrams(string_1)
    bigrams_s2 = get_bigrams(string_2)

    return len(bigrams_s1.intersection(bigrams_s2)) / len(bigrams_s1.union(bigrams_s2))


def get_bigrams(s):
    result = set()

    for i in range(len(s) - 1):
        result.add(s[i] + s[i+1])

    return result


# Tests
print(test_bigrams_jaccard("John Doe", "Jane Doe", 3 / 11))
print(test_bigrams_jaccard("John Doe", "John Doe", 7 / 7))
print(test_bigrams_jaccard("Jonathan Doe", "John Doe", 5 / 13))

Additional material

The runnable Python file is available online.