#first example
a = "Hello, World!"
print(a.upper())
#second example
a = "Hello, World!"
print(a.lower())
#thrid exam
a = " Hello, World!        "
print(a.strip()) # returns "Hello, World!
#fourth_exam
a = "Hello, World!"
print(a.replace("H", "J"))
#fifth_ex
a = "Hello, World!"
print(a.split("o")) # returns ['Hello', ' World!']
a = "Hello"
b = "World"
c = a + " " + b
print(c)