writing consecutive data to subprocess command 'more'

SanPy jhmsmits at gmail.com
Sat May 2 23:00:44 CEST 2009


Thanks, that works beautifully!

Regards,
Sander

On 2 mei, 22:35, "Gabriel Genellina" <gagsl-... at yahoo.com.ar> wrote:
> En Sat, 02 May 2009 15:53:17 -0300, SanPy <jhmsm... at gmail.com> escribió:
>
>
>
>
>
> > I have this method that prints a given text via a subprocess command
> > 'more' . It is like this:
>
> > def print_by_page(text):
> >     if hasattr(sys.stdout, 'isatty') and sys.stdout.isatty():
> >         viewer = 'more -EMR'
> >         proc = subprocess.Popen([viewer], shell=True,
> > stdin=subprocess.PIPE,
> >             stderr=subprocess.PIPE)
> >         try:
> >             stdout, stderr = proc.communicate(text)
> >         except OSError:
> >             pass
> >         else:
> >             if stderr: # probably no 'more' available on this system
> >                 sys.stdout.write(text)
> >             return
> >     sys.stdout.write(text)
>
> > It works fine, but what I really want to do is first print a header
> > through the 'more' command, then fetch some data from the web, and
> > show it through the same 'more' command/process. And even more data,
> > another header, other data from the web, all through the same 'more'
> > command/process.
> > Can somebody help me out on this?
>
> communicate writes to the child's stdin and waits for it to finish. If you  
> want to keep writing, don't use communicate. And you'll need to keep state  
>  from one call to another, so use a class. Based on the code above, create  
> a class Pager with __init__, write and close methods:
>
> class Pager:
>   def __init__(self):
>    # copy the logic above
>    self.proc = subprocess.Popen(...)
>    self.file = self.proc.stdin
>    # if something goes wrong, set self.proc=None and self.file=sys.stdout
>
>   def write(self, text):
>    self.file.write(text)
>
>   def close(self):
>    if self.proc:
>     self.file.close()
>     self.proc.wait()
>
> Also, take a look at the pager function in the pydoc module (see the  
> source) - it handles several cases.
>
> --
> Gabriel Genellina




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