On Mon, Jan 26, 2009 at 12:44 AM, anatoly techtonik <techto...@gmail.com> wrote: > You can't launch a process and communicate with it without blocking at > some point. The scenario where you can periodically check output and > error pipes without blocking and send input is not supported. > > Scenario One: control console program. This implies reading from input > and writing replies asyncronously > - Popen.stdin, stdout, stderr - stdin.write(), stdout.read() or > stderr.read() block script execution if any of the other OS pipe > buffers fills up and blocks the child process. Advice is to use > communicate(), but it waits for process to exit and hence doesn't > allow to send the input based on reply from previous send. > > Scenario Two: waiting for process that terminates with extensive output blocks > - Popen.wait() blocks if the child process generates enough output to > a stdout or stderr pipe, advice is to use Popen.communicate() > http://docs.python.org/library/subprocess.html#subprocess.Popen.wait > - Popen.communicate() - Waits for process to terminate, reads data > from stdout and stderr until end-of-file. Cashes data in memory - > should not be used for if the data size is large or unlimited. > > Solution - read(maxsize) and write(maxsize) functions that will return > immediately.
Hi Anatoly -- thanks for clarifying your issues. I hope other developers more familiar with subprocess.py will chime in and either help you figure out a way to do this without changes to the subprocess module, or, if that would be too painful, help you develop additional APIs. You could start by proposing a set of changes to subprocess.py and submit them as a patch to bugs.python.org; that is easier to deal with than pointing to a recipe on the Activestate site. -- --Guido van Rossum (home page: http://www.python.org/~guido/) _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
