My idea of what Python 3's range(begin, end, step) looks like

range.py

def range(begin, end = None, step = 1):
	if step == 0: 
		raise Exception("Step size cannot be 0")
	if end == None:
		end, begin = begin, 0
	while (abs(begin + step - end)) <= (abs(begin - end)):
		yield begin
		begin += step
 
assert(list(range(10)) == [0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
assert(list(range(0,10)) == [0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
assert(list(range(10, 0, 1)) == [])
assert(list(range(0, 10, 1)) == [0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
assert(list(range(0, 10, -1)) == [])
assert(list(range(10, 0, -1)) == [10, 9, 8, 7, 6, 5, 4, 3, 2, 1])