what is the difference between when to use "" and when to use ?
"" is an empty string while
 is an empty list. depending on what you need to manipulate you’ll want to create one or the other. it really depends on what you’re trying to do.
def reverse(text): s =  index = len(text)-1 while index >= 0: s.append(text[index]) index-=1 return ''.join(s)
here we use an empty list
s because we want to
.append() the letters of
text to the list in reverse order and
.join() to convert the list to a string and reach our desired output.
if we want to do the same by using strings, we’ll create an empty string
s = ""
def reverse(text): s = "" index = len(text)-1 while index >= 0: s += text[index] index -= 1 return s
in this example instead of using python list operations join and append we used the python string operation concatenate via the + operator. we started with an empty string
s and concatenated [added at the end] the letters of
text in reverse order.
hope it made sense and feel free to ask more questions