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RE: subprocess.Popen instance hangs

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  RE: subprocess.Popen instance hangs "Prasad, Ramit" <ramit.prasad@jpmorgan.com.dmarc.invalid> - 2013-08-29 18:49 +0000

#53252 — RE: subprocess.Popen instance hangs

Tim Johnson
> using Python 2.7.1 on OS X 10.7.5
> 
> I'm managing a process of drush using an instance of subprocess.Popen
> 
> The process has a '--verbose' option. When that option is passed as
> part of the initializer `args' argument, the process will hang.
> 
> It should be no surprise as drush output with the --verbose option
> can be _extremely_ verbose, and I can do without it, but I would
> like to learn how to handle it. I've googled this topic, but my poor
> little brain is yet to sort out all of the content found.
> 
> ## my relevant code follows :
> p = subprocess.Popen(args,stderr=subprocess.STDOUT,stdout=subprocess.PIPE)
> ## wait() is 'forever' if '--verbose' used
> exit_status = p.wait()
> output = p.stdout.read()
> ## done
> 
> I 'suspect' that using a tempfile may be the solution, if so, I
> could use some examples.
> 
> thanks
> --
> Tim
> tim at tee jay forty nine dot com or akwebsoft dot com
> http://www.akwebsoft.com
> --


I think the documentation covers your issue. 

"""
Popen.wait()
    Wait for child process to terminate. Set and return returncode attribute.
    Warning: will deadlock when using stdout=PIPE and/or stderr=PIPE and the child 
    process generates enough output to a pipe such that it blocks waiting for the 
    OS pipe buffer to accept more data. Use [Popen.]communicate() to avoid that.
""" From http://docs.python.org/2/library/subprocess.html#subprocess.Popen.wait

Does switching to `p.communicate()` solve your problem?


~Ramit



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