怎么反向索引数字第一张图是效果第二章是我做的

一直不能反向 那个0也是一直在的，第一张图是效果第二章是我做的

img

img

var1要先赋值成-13，然后每次+1，你从0每次-1不就是现在的效果吗


source = "Hello Python!"
# var = "Helto Python!"
start =0
var1= 0
print("正常索引>>>")
for c in source:
    print(f"{start:<4}",end=" ")
    start+=1
print()

for c in source:
    print(f"+---",end="")
print("+")
for c in source:
    print(f"{c:<4}",end=" ")
print()
for c in source:
    print(f"+---",end="")
print("+")
num = len(source)
for c in range(num):
    print(f"{c-num:<4}",end='')
    # var1 -= (2-1)
print()
print("           反向索引< < <")