From what I recall, PyPy has special optimizations on built-in types like ints and lists, which is great because they are very common, and it would be wasteful to treat an int like any other object.

If I subclass int specifically, for example

class bitset(int):
    def in_bit(self, i):
        return bool(self & (1 << i))

are these optimizations lost? I do not want to pre-maturely optimize, but I also don’t want to be wasteful since I can easily define a function like in_bit(b, i) instead.