how to change case in python code example

Example 1: python convert string to lowercase

# By Alan W. Smith and Petar Ivanov
s = "Kilometer"
print(s.lower())

Example 2: converting capital letters to lowercase and viceversa in python

s=input()
new_str=""
for i in range (len(s)):
    if s[i].isupper():
        new_str+=s[i].lower()
    elif s[i].islower():
        new_str+=s[i].upper()
    else:
        new_str+=s[i]
print(new_str)

Example 3: how do you change a string to only uppercase in python

original = Hello, World!

#both of these work
upper = original.upper()
upper = upper(original)