On 11Aug2010 00:11, RG <rnospa...@flownet.com> wrote: | When stdin is not a tty, Python seems to buffer all the input through | EOF before processing any of it: | | [...@mickey:~]$ cat | python | print 123 | print 456 <hit ctrl-D here> | 123 | 456 | | Is there a way to get Python to process input line-by-line the way it | does when stdin is a TTY even when stdin is not a TTY?
What you're seeing here is not python's behaviour but cat's behaviour. Almost all programs do line buffering (flush buffer at newline) when the file is a terminal (character device) and block buffering (flush when a fixed size buffer, typically 8192 bytes or some larger power of 2) when the file is not a terminal. This is default behaviour for the stdio package. So "cat" is simply not feeding any data to python until it has a lot of it; there is nothing python can do about that. We would need to know more about your specific task to suggest workarounds. Usually you either need an option on the upstream program to tell it to line buffer explicitly or you need to play silly games with pseudo terminals to convince the upstream program it is attached to a terminal. The latter is both ugly and generally inadvisable because many programs that change their buffering when attached to a terminal also change other behaviour, such as issuing interactiove prompts etc. Cheers, -- Cameron Simpson <c...@zip.com.au> DoD#743 http://www.cskk.ezoshosting.com/cs/ The type syntax for C is essentially unparsable. - Rob Pike -- http://mail.python.org/mailman/listinfo/python-list
