a = "hello, world!"
print(a.upper()) # this method for change lower to uppercase in string.

b = "HAI WORLD"
print(b.lower()) # this method for change upper to lowercase in strings.

d = "    Hello, World!    "
print(d.strip()) # remove the extra space returns "Hello, World!"

e = "Hello, World!"
print(e.replace("H", "J")) # this method replace method.

a = "Hello, World!"
print(a.split(",")) # this method split the strings returns ['Hello', ' World!'].
