Explaining `range` objects

myrange.py

class Range:
    def __init__(self, start, stop, step=1):
        self.start = start
        self.stop = stop
        self.step = step
    def __getitem__(self, index):
        result = self.start + index*self.step
        if result >= self.stop:
            raise IndexError("Index out of range")
        return result
    def __len__(self):
        """
        See https://github.com/python/cpython/blob/8dfe15625e6ea4357a13fec7989a0e6ba2bf1359/Objects/rangeobject.c#L890
        """
        return 1 + (self.stop - self.start - 1) // self.step
    def __repr__(self):
        return f"Range({self.start}, {self.stop}, {self.step})"
    def __iter__(self):
        return RangeIterator(self)

class RangeIterator:
    def __init__(self, rng):
        self._rng = rng
        self._current_index = 0
    def __iter__(self):
        return self
    def __next__(self):
        try:
            value = self._rng[self._current_index]
        except IndexError:
            raise StopIteration
        self._current_index += 1
        return value