matchtoolz

utilities for structural pattern matching

re.match

The Regex helper provides a convenient way to use regular expressions in Python's structural pattern matching. It allows you to match strings against regex patterns within match statements. There is als RegexBytes for bytes based regular expressions.

Example:

match Regex("hello"):
    case r"world":
        assert False
    case r"^h.?l+o$":
        assert True
    case _:
        assert False

__contains__

The IsIn and Contains helpers assist in membership tests.

IsIn is the "match" side helper

The IsIn helper is probably the easier to use for most use cases, but it may be less performat than Contains. IsIn checks for membership in the collection without modification, so you may be looking at O(1) for lookups.

lotr = Characters(hobbits, dwarves)

match IsIn("Frodo"):
    case lotr.hobbits:
        assert True
    case lotr.dwarves:
        assert False
    case _:
        assert False

Contains is the "case" side helper

Contains attempts to conver the collection to a frozenset, so for re-used lookups this will be more performant, but you have to build the set, so it isn't worth it unless the collection will be matched multiple times.

lotr = Characters(Contains(hobbits), Contains(dwarves))

match "Frodo":
    case lotr.hobbits:
        assert True
    case lotr.dwarves:
        assert False
    case _:
        assert False