Loop - Reversed List challenge - why not 'else'?

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#1

Hi all, I have a quick question on the answer to the Reversed list challenge in the Loops module
https://www.codecademy.com/courses/learn-python-3/lessons/python-functions-loops-cc/exercises/reversed

The challenge is:
Create a function named reversed_list() that takes two lists of the same size as parameters named lst1 and lst2 .

The function should return True if lst1 is the same as lst2 reversed. The function should return False otherwise.

For example, reversed_list([1, 2, 3], [3, 2, 1]) should return True .

and the correct code for the answer is:

def reversed_list(lst1, lst2):
  for index in range(len(lst1)):
    if lst1[index] != lst2[len(lst2) - 1 - index]:
      return False
  return True

My question is: why do we just say “return True” at the end, instead of “else return True”?

Thanks!

#2

This is because after the for loop, if the return False has not been reached, the return True will be reached due to the flow of the program. else is only used if you want something to be run after the if-but only if the if is false:

if 1 != 1:
  print("1 != 1")
else:
  print("1==1")
print("This program has ended")

In the case above, you want This program has ended to run regardless of the result of the if condition, but you still want a verdict of whether 1==1.

#3

Thanks for the response. Following your logic: don’t we want “return True” to run only if the if condition is false?

#4

Yes, but it needs to be out of the loop, otherwise the function will return a value on the first iteration-and that wouldn’t check the whole list-just the first element:

for index in range(len(lst1)):
  if lst1[index] != lst2[len(lst2) - 1 - index]:
   return  False
  else:
   return True

Image passing in these lists:

reversed_list([1, 2, 3], [3, 3, 1])

The first iteration would check to see if the first element of the first list (1) equals the last element of the second list (2). Then, since you have the else within the loop, the function would return True, even though these lists aren’t the reverse of eachother.