范围 function 的停止值背后的逻辑是什么，python 中的步长值为负

Question

My question is very simple. I'm new to python and I recently learnt about range() in python. And I go through an sample program in that problem they asked to print reverse multiplication table of 3 using range function And my code is

for i in range(30,3,-3):
           print(i)

But the output is not same as I expected. The output does not included 3. I don't know why. My question the last value should be (stop value -1) ie, 2 in this case. So 3 should also to be printed but not so. Please explain why. Does I misunderstood the logic? If so please explain.

Answer 1

The python docs for range(start, stop[, step]) says the following: :

For a negative step, the contents of the range are still determined by the formula r[i] = >start + step*i, but the constraints are i >= 0 and r[i] > stop.

This means the stop argument isn't included in the range calculation.

Answer 2

range() excludes the stop point when generating your list (well actually they return a generator). You should change 3 to 2 , then it will include 3