upper can be used to make a string or variable upper case. In this example, "Hello World" will become "HELLO WORLD".

#!/usr/bin/python
foo="Hello World"
print(foo.upper())

lower can be used to make a string or variable lower case. In this example, "Hello World" will become "hello world".

#!/usr/bin/python
foo="Hello World"
print(foo.lower())

capitalize can be used to the first character upper case. In this example, "hello world" will become "Hello world".

#!/usr/bin/python
foo="hello world"
print(foo.capitalize())

Here is how you can update a variable to be upper, lower, or capitalize.

#!/usr/bin/python
foo="Hello World"
foo = foo.lower()