progress bar and loop

[Martynas Jocius <mjoc delfi lt>]

Hello,

I'm writing a program in python and I'm using pygtk. I found a problem and
couldn't find a solution on the web, so I decided to look for help in gtk
hackers mailing list.

There is a window with it's widgets and progress bar. There is an array of
commands and these commands are executed while the loop.

For example, the array is:
["mpg123 track1.mp3 -w track1.wav",
 "mpg123 track2.mp3 -w track2.wav",
 "mpg123 track3.mp3 -w track3.wav"]

These commands do the execution of mpg123, which converts mp3 files to wav.

The simplified code is some like that:
# ---
i = 0
while i < 3:

   add_timeout(...)
   # adding progress bar timeout here
   
   # The program forks here and child process executes a command from
   # the array:
   [...]
   fork...
   [...]
      # child
      exec array[i]
      exit when done

   i += 1

def add_timeout(...):
   # while executing a command, wav file size grows up
   # progress bar show the size (current_size / full_size)

The problem is:
while executing a shell command, the while loop should not add new timeouts
   and execute next shell commands. So it can continue() until exec process
   is alive. 
But if I do so, the gtk window hangs and stops, and loop makes a very big
CPU usage. sleep() doesn't help for GUI application. 

If someone knows what to do or can give some links about that, please help.
I know few programs (like grip) where the task as mine works very well, but C
code is too hard to understand for me, I'm searching for some examples for
loops and progress bars.

Thanks.

--
Martynas Jocius
http://mjoc.infoseka.lt