range.py

def range(start, stop=None, step=None):
    result = []
    s = 1
    if step is not None:
        s = step
    if stop is not None:
        while True:
            if start < stop:
                result.append(start)
                start += s
            else:
                break
    else:
        stop, start = start, 0
        while True:
            if start < stop:
                result.append(start)
                start += s
            else:
                break
    return result