Passing optional arguments from optparse
===

I'm trying to figure out how to pass optional arguments from optparse. The problem I'm having is if an optparse option is not specified, it defaults to a None type, but if I pass the None type into a function, it yells at me instead of using the default (Which is understandable and valid). 

    conn = psycopg2.connect(database=options.db, hostname=options.hostname, port=options.port)

The question is, how do I use the function's defaults for optional arguments but still pass in user inputs if there is an input without having a huge number of if statements.