Crimes with Python's pattern matching

Looking in the implementation of the Python version of ABC[0], you'll see that `__subclasshook__` doesn't do any language magic, it just registers the method to be called in `__instancecheck__`. So if you just implement `__instancecheck__` directly, you get the same behavior, but without the caching around it. class OneWayMeta(type): seen_classes = set() @classmethod def __instancecheck__(cls, instance): C = instance.__class__ print(f"trying {C}") if C in cls.seen_classes: return False cls.seen_classes |= {C}…

My favorite Python "crime" is that a class that defines __rrshift__, instantiated and used as a right-hand-side, lets you have a pipe operator, regardless of the left-hand-side (as long as it doesn't define __rshift__). It's reasonably type-safe, and there's no need to "close" your chain - every outputted value as you write the chain can have a primitive type. x = Model.objects.all() >> by_pk >> call(dict.values) >> to_list >> get('name') >> _map(str.title) >> log_debug >> to_json It shines in notebooks…