Python Interactive Shell - outputting to stdout?

[Avi Berkovich]

Hey Steve,

Well, I've tried flush() before, but I didn't know about the "-u" switch.

Thank you for tinkering on this, I shall post again if I make any progress.

Avi


Steve Holden wrote:
> Steve Holden wrote:
> 
>> Avi Berkovich wrote:
>>
>>> Hey,
>>>
>>> I can't make it work, I don't get any data from either stdout nor 
>>> stderr.
>>> If I send lines and then close the stdin pipe, I may get an exception 
>>> message from several lines up.
>>>
>>> I tried manually reading from the stdout pipe, but it just blocks and 
>>> hangs no matter what I send over via the stdin pipe.
>>>
>>> This behavior isn't presented by the command line interpreter by any 
>>> chance.
>>>
>>> Any suggestions?
>>
>>
>>
>> Yes: post your code along with messages (if any)!
>>
>> regards
>>  Steve
> 
> 
> Sorry, for some reason I can no longer find the message you posted the 
> code in -- it didn't get correctly threaded in Mozilla. Anyway, I can't 
> say that I exactly understand what's going on, but here are a couple of 
> observations:
> 
> 1. The interpreter performs buffering even when running in interactive 
> mode unless it can see a terminal (which here it can't). Hence adding a 
> "-u" to the interpreter command line is useful.
> 
> 2. There's a problem with your stop condition, which is why the attached 
> modified version sleeps before closing the pipe to the interpreter.
> 
> import threading
> import sys
> import popen2
> 
> class Piper(threading.Thread):
> 
>    def __init__(self, readPipe, output):
>        threading.Thread.__init__(self)
> 
>        if not isinstance(readPipe, file):
>            raise TypeError, "readPipe parameter must be of File type"
>        #if not isinstance(output, file):
>        #    raise TypeError, "output parameter must be of File type"
> 
>        self.readPipe = readPipe
>        self.output = output
>        self.toStop = False
> 
>    def run(self):
>        print "Running"
>        while not self.toStop and not self.readPipe.closed:
>            read = self.readPipe.readline()
>            self.output.write(read)
>            self.output.flush()
>        print "Stopped"
> 
>    def stop(self):
>        self.toStop = True
> 
> 
> if __name__ == "__main__":
>    r, w = popen2.popen4('c:\\python24\\python.exe -u')
>    piper = Piper(r, sys.stdout)
>    piper.start()
>    w.write("print 'Hello!'\r\n")
>    w.flush()
>    w.write("print 'Goodbye!'\r\n")
>    w.flush()
>    import time; time.sleep(2)
>    w.close()
>    #import time; time.sleep(3)
>    #r.close()
>    piper.stop()
> 
> Various other bits and pieces of messing about didn't really yield any 
> useful conclusions, so I pass this on only in the hope that you may be 
> more motivated to follow up now you can actually see some interpreter 
> output. I would have thought the flush() calls would have made output 
> appear one line at a time, but sadly they do not.
> 
> regards
>  Steve