Fill as list (with conditions).

[wavic]

You are modifying the list on the go during the for loop. This is not a good idea. I admit that I am unable to see what is going on looking at the script.

If you want to play with the index you can use enumerate.

for index, element in enumerate([4,3,2,1,0]):
    print(index + 1, element)

Output:
1 4
2 3
3 2
4 1
5 0