I'll be checking out some of these other scripts for performance. My concept - I thought it'd be fun to build off of the list index in my loop. It works. ChatGPT claimed that this list-driven syntax will have better performance than string concatenation, e.g. the += letter.lower() syntax.

def swap_case(s): newstring = list(s) # Create an empty string to store the new text

for index in range(len(newstring)):
    if newstring[index].isupper():
       newstring[index]= newstring[index].lower()
    else: 
        newstring[index]= newstring[index].upper()
return ''.join(newstring)  #Combining the separate characters back into a string

if name == 'main': s = input() result = swap_case(s) print(result)