On Sun, Dec 9, 2012 at 7:14 AM, Glyph <gl...@twistedmatrix.com> wrote:
> On Dec 7, 2012, at 5:10 PM, anatoly techtonik <techto...@gmail.com> wrote: > > What about reading from other file descriptors? subprocess.Popen allows >> arbitrary file descriptors to be used. Is there any provision here for >> reading and writing non-blocking from or to those? > > > On Windows it is WriteFile/ReadFile and PeekNamedPipe. On Linux it is > select. Of course a test is needed, but why it should not just work? > > > This is exactly why the provision needs to be made explicitly. > > On Windows it is WriteFile and ReadFile and PeekNamedPipe - unless the > handle is a socket in which case it needs to be WSARecv. Or maybe it's > some other weird thing - like, maybe a mailslot - and you need to call a > different API. > IIRC on Windows there is no socket descriptor that can be used as a file descriptor. Seems reasonable to limit the implementation to standard file descriptors in this platform. On *nix it really shouldn't be select. select cannot wait upon a file > descriptor whose *value* is greater than FD_SETSIZE, which means it sets > a hard (and small) limit on the number of things that a process which wants > to use this facility can be doing. > I didn't know that. Should a note be added to http://docs.python.org/2/library/select ? I also thought that poll acts like, well, a polling function - eating 100% CPU while looping over inputs over and over checking if there is something to react to. > On the other hand, if you hard-code another arbitrary limit like this into > the stdlib subprocess module, it will just be another great reason why > Twisted's spawnProcess is the best and everyone should use it instead, so > be my guest ;-). > spawnProcess requires a reactor. This PEP is an alternative for the proponents of green energy. =)
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