changing upper and lowercase in python code example

Example 1: 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 2: python 3 calculate uppercase lowercase letter

world = input()
upper,lower = 0,0

for i in world:
    upper+=i.isupper()
    lower+=i.islower()

print("UPPER CASE {0}\nLOWER CASE {1}".format(upper,lower))