Make the string upper case or lower case

Info:

Sometmes, according to the needs, you may want to make a string all upper-case or all lower-case. You can modify it easily this way.

Example:

greeting = "Hello World!"
print(greeting.upper())

will give this output:

HELLO, WORLD!

What if you want to make it lower-case?

greeting = "Hello, World!"
print(greeting.lower())

will give this output:

hello, world!