Simple GRC/Python questions

I am new to GNU Radio and am very niave to object oriented programming
(although i am learning at a decent pace).

what i am trying to do is to calculate the BER of a system with
incrementing amounts of AWGN to determine the minimum amount of power i
will be able to use in my system. I would like to have the python code
output the amplitude of the AWGN to a file in increments of about .001,
run the program having it also output the BER that goes with it. then
increase the amplitude again by .001 and do it again and again in a
loop. however i cant seem to output lists of those numbers nor for that
matter can i even make the code compute past the default value of the
amplitude.

with that said, i need some help. When i generate a python code from the
GRC it ends with:

if name == ‘main’:
try:
parser = OptionParser(option_class=eng_option, usage="%prog:
[options]")
(options, args) = parser.parse_args()
tb = ber_sim()
tb.Run(True)

the reason for use .run() the gui will display if you py file is
modified by a grc file, but if use the .start() function, no gui display
even in same program.

how can I add some logic after the program started?
I mean if I use start() function ,the code after start() could be
executed
(use run function these code could not be executed),but the GUI silde or
ratiobottom item which add to file by GRC previously could not be
displayed?

Is there anyway to have both GUI item and some logic after program could
be
available in same time? od does it even matter if the GUI is displayed
as long as i am able to output information to a file that i can read?

which brings me to the next question, how would i output that
information to a file that i can read?

alsoooooo what is that parser thing doing? i dont understand what it and
the next line are doing to the program…