[Tutor] reading from stdin

Peter Markowsky peterm at ccs.neu.edu
Wed Mar 2 00:15:19 CET 2005


On Mar 1, 2005, at 6:01 PM, Sean Perry wrote:

> jfouhy at paradise.net.nz wrote:
>> If I do:
>> $ ./produce.py | ./read.py
>> I get nothing for ten seconds, then I get the numbers 0 through 9, 
>> one per line.
>> What am I missing?
> From the python man page:
> -u
>     Force stdin, stdout and stderr to be totally unbuffered. On 
> systems where it matters, also put stdin, stdout and stderr in binary 
> mode. Note that there is internal buffering in xreadlines(), 
> readlines() and file-object iterators ("for line in sys.stdin") which 
> is not influenced by this option. To work around this, you will want 
> to use "sys.stdin.readline()" inside a "while 1:" loop.

What exactly is the "right" way to put sys.stdin in unbuffered mode?

in another program I've tried to accomplish that by  doing something 
like this

import os
import fcntl


stdinfd = sys.stdin.fileno()
fcntl.fcntl(stdinfd, fcntl.F_SETFL, os.O_NONBLOCK)


and then calling  later

data = sys.stdin.read(numbytes)

is this correct?


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