Get a signal once a subprocess ends

问题:

I am using the subprocess.Popen function to run a command line. Without having to use Popen.wait(), I want to check the subprocess after it has finished using Popen.poll(). Any suggestions on how to do this?

import subprocess
job = subprocess.Popen('command line', shell = True)
print(job.poll())

As it is, I get job.poll() printed before the subprocess starts. I want it to wait until it ends. I don't want to use wait because the rest of the user interface becomes unusable until the process ends. This is in PyQt4.

回答1:

As Python - wait on a condition without high cpu usage says, there are only two ways in existence to wait for something: polling or setting up/using a notification system.

If it's UI - didn't you forget about one notification system you always have - the message queue?

Besides, you can always (and, if it's UI, should always) perform any time-consuming tasks in worker threads. If which case, you are just fine with a synchronous call.