Turn your argparse-parser into an interactive session, prompting the user for the defined arguments.
$ ./example.py
A random string: a value here
One of these values (legal values are legal1, legal2): legal
legal1 legal2
One of these values (legal values are legal1, legal2): legal1
Some integer: a
>>> Error: Value has to be <type 'int'>
Some integer: 10
Some other integer: 101
Resulting arguments namespace: Namespace(a4=101, argument_one='a value here', argument_three=10, argument_two='legal1')