#set all the defaults first
DBName = "mythconverg"
DBUserName = "mythtv"
DBPassword = "mythtv"

#list of arguments that can be passed:
acceptedArgs = ['--DBName','--DBUserName']

#pretend these are our arguments for now
myargs = ['--DBName="newName"','--DBUserName="newUser"','--DBPassword="newPassword"']

for arg in myargs:
    if arg.split['='][0] in acceptedArgs:
        #assign new value here
    else
        #this is an unacceptable argument, raise an exception