Feature Requests item #1191964, was opened at 2005-04-28 13:40 Message generated for change (Comment added) made by josiahcarlson You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=355470&aid=1191964&group_id=5470
Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: None Group: None Status: Open Resolution: None Priority: 5 Submitted By: Josiah Carlson (josiahcarlson) Assigned to: Peter Åstrand (astrand) Summary: asynchronous Subprocess Initial Comment: It would be terribly nice if the Popen class in the subprocess module would allow a programmer to easily say "send some data right now (if I have some to send) and receive whatever information is available right now". Essentially the equivalent of asyncore.loop(count=1), only that it returns the data received, instead of placing it in a buffer. Why would this functionality be useful? Currently, when using the subprocess module with pipes, the interaction with a pipe is limited to "send data if desired, close the subprocess' stdin, read all output from the subprocess' stdout, ...". Certainly one can pull the pipes out of the Popen instance, and perform the necessary functions on posix systems (with select or poll), but the additional magic on WIndows is a little less obvious (but still possible). There is a post by Paul Du Bois with an example using win32pipe.PeekNamedPipe: http://groups-beta.google.com/group/comp.lang.python/msg/115e9332cc1ca09d?hl=en And a message from Neil Hodgeson stating that PeekNamedPipe works on anonymous pipes: http://mail.python.org/pipermail/python-dev/2000-May/004200.html With this modification, creating Expect-like modules for any platform, as well as embedded shells inside any GUI with a text input widget, becomes easy. Heck, even Idle could use it rather than a socket for its interactive interpreter. ---------------------------------------------------------------------- >Comment By: Josiah Carlson (josiahcarlson) Date: 2005-09-21 13:51 Message: Logged In: YES user_id=341410 I've implemented this as a subclass of subprocess.Popen in the Python cookbook, available here: http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/440554 Essentially this is a request for inclusion in the standard library for Python 2.5 . ---------------------------------------------------------------------- Comment By: Josiah Carlson (josiahcarlson) Date: 2005-06-26 12:47 Message: Logged In: YES user_id=341410 How about if subprocesses have 3 new methods, send(input), recv(maxlen), and recv_stderr(maxlen). send(input) would perform like socket.send(), sending as much as it currently can, returning the number of bytes sent. recv(maxlen) and recv_stderr(maxlen) would recieve up to the provided number of bytes from the stdout or stderr pipes respectively. I currently have an implementation of the above on Windows and posix. I include the context diff against revision 1.20 of subprocess.py in current CVS. ---------------------------------------------------------------------- Comment By: Josiah Carlson (josiahcarlson) Date: 2005-05-28 17:15 Message: Logged In: YES user_id=341410 I suppose I should mention one side-effect of all this. It requires three more functions from pywin32 be included in the _subprocess driver; win32file.ReadFile, win32file.WriteFile, and win32pipe.PeekNamedPipe . Read and Peek are for reading data from stdout and stderr, and Write is for the support for partial writes to stdin. ---------------------------------------------------------------------- Comment By: Josiah Carlson (josiahcarlson) Date: 2005-05-28 16:22 Message: Logged In: YES user_id=341410 I've got a version of subprocess that has this functionality with pywin32. Making it work on *nix systems with usable select is trivial. About the only question is whether the functionality is desireable, and if so, what kind of API is reasonable. Perhaps adding an optional argument 'wait_for_completion' to the communicate method, which defaults to True for executing what is currently in the body of communicate. If the 'wait_for_completion' argument is untrue, then it does non-waiting asynchronous IO, returning either a 2 or 3-tuple on completion. If input is None, it is a 2-tuple of (stdout, stderr). If input is a string, it is a 3-tuple of (bytes_sent, stdout, stderr). How does that sound? ---------------------------------------------------------------------- Comment By: Dave Schuyler (parameter) Date: 2005-04-28 16:38 Message: Logged In: YES user_id=473331 More control of sub-processes would be great. Several times in the past few years I've done stuff with os.system, popenN, or spawn* and it would be useful to have even more cross-platform consistency and support in this area. Anyway, this is just a vote to encurage other developers. ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=355470&aid=1191964&group_id=5470 _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
