Do x after y increment

Question

I want to do something after i is 20, 40, etc.

For example:

i = 0
while True:
    i+=1
    if i == # increment of 20 (40, 60, 80, etc.):
        # do this

Answer 1

i = 0
while True:
    i+=1
    if i % 20 == 0: # increment of 20 (40, 60, 80, etc.):
        print(i) #or something else

Output:

20
40
60
80
...

Answer 2

Options 1 & 2 uses the modulus operator, to detect when i is a multiplication of 20, are less efficient as unnecessary iterations will happen.

Option 3 uses range, and more efficient as only necessary iterations will happen.

Option 1

Use not i % 20:

i = 0
while True:
    i+=1
    if not i % 20:
        print(i)

Option 2

Use 0 == i % 20:

i = 0
while True:
    i+=1
    if 0 == i % 20:
        print(i)

Option 3 : For Loop

Using range: start from 20 till threshold in jumps of 20

threshold = 10000
for i in range(20, threshold, 20):
    print(i)