Thanks for the suggestion.
For my script, I want to download a picture from internet & show it in a
window, that's why I use wxPython.
Well, I think I may can avoid sleep in wxPython in 2 ways:
1. Use web.py, let python do backend work, let browser show me everything. As
2. Write 2 scripts, one script do network related works, sleep at will; the
other one show GUI. Use pipe or socket for process communication.