why join() is not working here

Question

s=input("Enter string for reversed=")
l=len(s)
output=''
l=l-1
while l>=0:
output=output.join(s[l])
l=l-1
print(output)

Answer 1

This problem has been solved I recognise, but I just wished to mention that the function .reverse() exists, so the most concise code would be:
s=input().reverse()
print(s)

Answer 2

Just do:
output += s[l]

or if you want to optimize your whole code:
s = input()
s = s[::-1]
print(s)

Answer 3

Add a '+=' instead of '+' in the join line of code:

while l>=0:
output += output.join(s[l])
l=l-1
print(output)

Answer 4

join() returns a string, I think the problem this is. And you don't have to use join.

s=input("Enter string for reversed=")

l=len(s)
output=""
l = l - 1

while l>=0:
output = output + s[l]
l=l-1

print(output)

It must also work. I hope, it helps. Happy coding!