Replicate of python range class in Python Class `Range` to understand how it works under the hood.

Range.py

class Range:
    def __init__(self, start, stop=None, step=1):
        if step == 0:
            raise ValueError("Step can not be zero.")

        if stop is None:
            start, stop = 0, start

        # calculate the effective length once
        self.length = max(0, ((stop - start) + (step - 1)) // step)

        self.start = start
        self.step = step
        self.stop = stop

    def __str__(self):
        return "Range(" + str(self.start) + ", " + str(self.stop) + ", " + str(self.step) + ")"

    def __len__(self):
        return self.length

    def __getitem__(self, item):
        if item < 0:
            item += len(self)

        if item >= self.length:
            raise IndexError("Range object index out of range")

        return self.start + item * self.step


if __name__ == "__main__":
    r = range(8, 140, 5)
    R = Range(8, 140, 5)

    print(list(r))
    print(list(R))
    print(len(r))
    print(len(R))