background function in Python

Question

I\'ve got a Python script that sometimes displays images to the user. The images can, at times, be quite large, and they are reused often. Displaying them is not critical, b

Answer 1

I prefer to use gevent for this sort of thing:

import gevent
from gevent import monkey; monkey.patch_all()

greenlet = gevent.spawn( function_to_download_image )
display_message()
# ... perhaps interaction with the user here

# this will wait for the operation to complete (optional)
greenlet.join()
# alternatively if the image display is no longer important, this will abort it:
#greenlet.kill()

Everything runs in one thread, but whenever a kernel operation blocks, gevent switches contexts when there are other "greenlets" running. Worries about locking, etc are much reduced, as there is only one thing running at a time, yet the image will continue to download whenever a blocking operation executes in the "main" context.

Depending on how much, and what kind of thing you want to do in the background, this can be either better or worse than threading-based solutions; certainly, it is much more scaleable (ie you can do many more things in the background), but that might not be of concern in the current situation.