a = [4,7,3,8,2,5,1,9,0]

i = 4
j = len(a)-1
while i < j:
    temp = a[i]
    a[i] = a[j]
    a[j] = temp
    i += 1
    j -= 1

a

[4, 7, 3, 8, 0, 9, 1, 5, 2]

def reverse(animal):
    i = 0
    j = len(animal)-1
    while i < j:
        temp = animal[i]
        animal[i] = animal[j]
        animal[j] = temp
        i += 1
        j -= 1
    return(''.join(animal))

my_string = "cat lion tiger dragon" 

test = [reverse(list(animal)) for animal in my_string.split(' ')]

test

['tac', 'noil', 'regit', 'nogard']