Prior to this,I run two command in for loop,like for x in $set: command In order to save time,i want to run these two command in the same time,like parallel method in makefile
Thanks Lyn
3 Answers
The threading module won't give you much performance-wise because of the Global Interpreter Lock.
I think the best way to do this is to use the subprocess module and open each command with it's own stdout.
processes = {}
for cmd in ['cmd1', 'cmd2', 'cmd3']:
p = subprocess.Popen('cmd1', stdout=subprocess.PIPE)
processes[p.stdout] = p
while len(processes):
rfds, _, _ = select.select(processes.keys(), [], [])
for fd in rfds:
process = processses[fd]
print fd.read()
if process.returncode is not None:
print "Process {0} returned with code {1}".format(process.pid, process.returncode)
del processes[fd]
You basically have to use select to see which file descriptors are ready and you have to check their returncode to see if doing a "read" caused them to exit. Processes basically go into a wait state until their stdout is closed. If you would like to do some things while you're waiting, you can put a timeout on select.select() so you'll stop waiting after so long. You can test the length of rfds and if it is 0 then you know that the timeout happened.
Comments
twisted or select module is probably what you're after.
If all you want to do is a bunch of batch commands, shell scripts, ie
#!/bin/sh
for i in "command1 command2 command3"; do
$i &
done
Might work better. Alternately, a Makefile like you said.
Comments
Look at the threading module.
subprocess.Popen()?