how do I fix this code - variable not defined in function

Question

I'm having trouble understand how to fix the below code so the function will print a_string in reverse. I know rev is not defined...just couldn't figure out how to make it work. Any help would be great, thanks.

def reverse(a_string):

  for i in range(len(a_string)-1, -1, -1):
    rev =rev+ a_string[i]
    return rev
reverse("cat")
print(rev)

Answer 1

I wonder, why don't you do it this way:

return a_string[::-1]

Unless you wanna do it manually in purpose, of course.

Answer 2

In order to define rev so python stores it as a string type: rev = "" So your code could look like this:

def reverse(a_string):
    rev = ""
    for i in range(len(a_string)-1, -1, -1):
        rev += a_string[i]
    return rev
print(reverse("cat"))

For the last line [print(rev)], you cannot print the rev variable since it is stored within the function and is not a global variable. So to print the function output you use: print(reverse("cat")).