cgi integration question 2

[Ken]

"Gerhard Häring" <gerhard.haering at gmx.de> wrote in message
news:slrnar5gqs.hg.gerhard.haering at lilith.my-fqdn.de...
> Ken wrote in comp.lang.python:
> > Hello, I have this problem which I don't know what it means or how
> > to fix, can someone help me?
> >
> > Traceback (most recent call last): File "chessboard.cgi", line 143, in ?
> > outf.close() IOError: [Errno 32] Broken pipe
>
> Dunno why, but I have a few remarks nonetheless.
>
> > Python frontend program:
> >   lines = []
> >   outf, inf = os.popen2("knight")
> >   print >>outf, size #size
> >   print >>outf, startX #start X position
> >   print >>outf, startY #start Y position
> >   outf.close()  #<<========= Refer to this line 143
> >   time.sleep(1)
>
> Frankly, sleeping in the context of synchronous IO doesn't make any
> sense.
>
> >   maxSize = string.atoi(size) * string.atoi(size)
> >   while len(lines)< maxSize:
> >     lines = inf.readlines() #Output produce by back end program ["34",
"35",
> > ...etc]
>
> readlines() reads the *whole* output, so if after that you read again,
> it will block forever. If you want to read line by line, use
> readline() instead. But read the docs about read() and readline(), as
> you'll find important info there, for example that if it returns an
> empty string it means that you've reached EOF :-)
>
> >     if len(lines)==maxSize:
> >       inf.close()
> >       break
> >     time.sleep(1)
>
> You could rewrite this as:
>
> outf, inf = os.popen2("night")
> print >>outf, ...
> ...
> outf.close()
> lines = inf.readlines()
> inf.close()
>
> -- Gerhard

Hi, I think my problem here is that the backend program can't output ontime
and I got an empty list in return. Does lines = inf.readlines() actually
wait for the backend program to finish execution before proceeding to
inf.close() ?

I find it very strange that when I compile using python scriptfile.cgi in
telnet environment, it works fine, but when I put on the web browser, the
list is empty. Do you know how I can fix this problem?

Thanks

==
My original program's segment:

size="3"
startX="2"
startY="1"
function = "3"

lines = []
if function=="3" and size!="" and startX!="" and startY!="":
  #Execute Backend program
  outf, inf = os.popen2("knight")
  print >>outf, size
  print >>outf, startX
  print >>outf, startY
  outf.close()
  lines = inf.readlines()

  print lines #empty on web browser, ok in telnet