timing_hash_function.py

import string
import timeit


class BadHash(str):
    def __hash__(self):
        return 42


class GoodHash(str):
    def __hash__(self):
        """
        This is a slightly optimized version of twoletter_hash
        """
        return ord(self[1]) + 26 * ord(self[0]) - 2619


if __name__ == "__main__":
    baddict = set()
    gooddict = set()
    for i in string.ascii_lowercase:
        for j in string.ascii_lowercase:
            key = i + j
            baddict.add(BadHash(key))
            gooddict.add(GoodHash(key))

    badtime = timeit.repeat(
        "key in baddict",
        setup="from __main__ import baddict, BadHash; key = BadHash('zz')",
        repeat=3,
        number=100_000,
    )
    goodtime = timeit.repeat(
        "key in gooddict",
        setup="from __main__ import gooddict, GoodHash; key = GoodHash('zz')",
        repeat=3,
        number=100_000,
    )

    print(f"Min lookup time for baddict: {min(badtime)}")
    print(f"Min lookup time for gooddict: {min(goodtime)}")

    # Results:
    #   Min lookup time for baddict: 17.719061855008476
    #   Min lookup time for gooddict: 0.42408075400453527