On Tue, 2005-03-22 at 12:49 +1200, Greg Ewing wrote: > Donovan Baarda wrote: > > > Consider the following. This is pretty much the only way you can use > > popen2 reliably without knowing specific behaviours of the executed > > command; > > > > ... > > fcntl.fcntl(child_in, fcntl.F_SETFL, flags | os.O_NONBLOCK) # \ > > ... # / > > fcntl.fcntl(child_out, fcntl.F_SETFL, flags | os.O_NONBLOCK)# \ > > I still don't believe you need to make these non-blocking. > When select() returns a fd for reading/writing, it's telling > you that the next os.read/os.write call on it will not block. > Making the fd non-blocking as well is unnecessary and perhaps > even undesirable.
Yeah... For some reason I had it in my head that os.read/os.write would not do partial/incomplete reads/writes unless the file was in non-blocking mode. > > For 1) and 2), note that popen2 returns file objects, but as they cannot > > be reliably used as file objects, we ignore them and grab their > > fileno(). Why does popen2 return file objects if they cannot reliably be > > used? > > I would go along with giving file objects alternative read/write > methods which behave more like os.read/os.write, maybe called > something like readsome() and writesome(). That would eliminate > the need to extract and manipulate the fds, and might make it > possible to do some of this stuff in a more platform-independent > way. The fact that partial reads/writes are possible without non-blocking mode changes things a fair bit. Also, the lack of fnctl support in Windows needs to be taken into account too. I still think the support for partial reads in non-blocking mode on file.read() is inconsistent with the absence of partial write support in file.write(). I think this PEP still has some merit for cleaning up this inconsistency, but otherwise doesn't gain much... just adding a return count to file.write() and clearing up the documented behaviour is enough to do this. The lack of support on win32 for non-blocking mode, combined with the reduced need for it, makes adding a "setblocking" method undesirable. I don't know what the best thing to do now is... I guess the readsome/writesome is probably best, but given that os.read/os.write is not that bad, perhaps it's best to just forget I even suggested this PEP :-) -- Donovan Baarda <[EMAIL PROTECTED]> http://minkirri.apana.org.au/~abo/ _______________________________________________ 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
