Did you notice the term re.IGNORECASE in the last example? Did you figure out its importance?

An expression's behavior can be modified by specifying a flag value. You can add flags as an extra argument to the different functions that you have seen in this tutorial. Some of the more useful ones are:

IGNORECASE (I) - Allows case-insensitive matches.
DOTALL (S) - Allows . to match any character, including newline.
MULTILINE (M) - Allows start of string (^) and end of string ($) anchor to match newlines as well.
VERBOSE (X) - Allows you to write whitespace and comments within a regular expression to make it more readable.