for i in range(start,stop,step) Python 3

Question

I want to list a range of numbers and I\'m using the \"for i in range(start,stop,step)\".

def range():
    P=36
    for i in range(P+1,0,-1):
        P=P-4
          


        

Answer 1

What's happening is that using range, creates you a list from 36 to 0 at the beggining and does a for loop 37 times. Your var P has no longer effect on the number of loops if you change it in your loop.

In your first case you'll have 36-37*4 = -112

In your second case you have your loop executed 9 times thats why you get 0 36 -9*4 = 0 :)

Try using xrange it should create a value for each loop and i think it will stop at 0.

Answer 2

To create a list from 36 to 0 counting down in steps of 4, you simply use the built-in range function directly:

l = list(range(36,-1,-4)) 
# result: [36, 32, 28, 24, 20, 16, 12, 8, 4, 0]

The stop value is -1 because the loop runs from the start value (inclusive) to the stop value (exclusive). If we used 0 as stop value, the last list item would be 4.

Or if you prefer a for loop, e.g. because you want to print the variable inside it:

for P in range(36,-1,-4):
    print(P)