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sys.stdout.detach() results in ValueError

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  sys.stdout.detach() results in ValueError Peter Kleiweg <pkleiweg@xs4all.nl> - 2012-03-07 20:41 +0100
    Re: sys.stdout.detach() results in ValueError Dave Angel <d@davea.name> - 2012-03-07 17:14 -0500
      Re: sys.stdout.detach() results in ValueError Peter Kleiweg <pkleiweg@xs4all.nl> - 2012-03-07 23:35 +0100
        Re: sys.stdout.detach() results in ValueError Terry Reedy <tjreedy@udel.edu> - 2012-03-07 19:10 -0500
          Re: sys.stdout.detach() results in ValueError Mark Tolonen <metolone@gmail.com> - 2012-03-07 16:41 -0800
    Re: sys.stdout.detach() results in ValueError Benjamin Peterson <benjamin@python.org> - 2012-03-08 03:49 +0000

#21334 — sys.stdout.detach() results in ValueError

I want to write out some binary data to stdout in Python3. I 
thought the way to do this was to call detach on sys.stdout. But 
apparently, you can't. Here is a minimal script:

    #!/usr/bin/env python3.1
    import sys
    fp = sys.stdout.detach()

Not yet using fp in any way, this script gives the following error:

    Exception ValueError: 'underlying buffer has been detached' in

Same in Python 3.1.4 and Python 3.2.2

So, what do I do if I want to send binary data to stdout? 



-- 
Peter Kleiweg
http://pkleiweg.home.xs4all.nl/

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#21358

On 03/07/2012 02:41 PM, Peter Kleiweg wrote:
> I want to write out some binary data to stdout in Python3. I
> thought the way to do this was to call detach on sys.stdout. But
> apparently, you can't. Here is a minimal script:
>
>      #!/usr/bin/env python3.1
>      import sys
>      fp = sys.stdout.detach()
>
> Not yet using fp in any way, this script gives the following error:
>
>      Exception ValueError: 'underlying buffer has been detached' in
>
> Same in Python 3.1.4 and Python 3.2.2
>
> So, what do I do if I want to send binary data to stdout?
>
>
>

sys.stdout.write(  some_binary_data )

Why should you need to do some funny manipulation?

If you have some other unstated motivation, better ask a clearer question.



-- 

DaveA

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#21359

Dave Angel schreef op de 7e dag van de lentemaand van het jaar 2012:

> On 03/07/2012 02:41 PM, Peter Kleiweg wrote:
> > I want to write out some binary data to stdout in Python3. I
> > thought the way to do this was to call detach on sys.stdout. But
> > apparently, you can't. Here is a minimal script:
> > 
> >      #!/usr/bin/env python3.1
> >      import sys
> >      fp = sys.stdout.detach()
> > 
> > Not yet using fp in any way, this script gives the following error:
> > 
> >      Exception ValueError: 'underlying buffer has been detached' in
> > 
> > Same in Python 3.1.4 and Python 3.2.2
> > 
> > So, what do I do if I want to send binary data to stdout?
> > 
> > 
> > 
> 
> sys.stdout.write(  some_binary_data )

TypeError: must be str, not bytes




-- 
Peter Kleiweg
http://pkleiweg.home.xs4all.nl/

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#21362

On 3/7/2012 5:35 PM, Peter Kleiweg wrote:
> Dave Angel schreef op de 7e dag van de lentemaand van het jaar 2012:
>
>> On 03/07/2012 02:41 PM, Peter Kleiweg wrote:
>>> I want to write out some binary data to stdout in Python3. I
>>> thought the way to do this was to call detach on sys.stdout. But
>>> apparently, you can't. Here is a minimal script:
>>>
>>>       #!/usr/bin/env python3.1
>>>       import sys
>>>       fp = sys.stdout.detach()
>>>
>>> Not yet using fp in any way, this script gives the following error:
>>>
>>>       Exception ValueError: 'underlying buffer has been detached' in
>>>
>>> Same in Python 3.1.4 and Python 3.2.2
>>>
>>> So, what do I do if I want to send binary data to stdout?
>>>
>>>
>>>
>>
>> sys.stdout.write(  some_binary_data )
>
> TypeError: must be str, not bytes

Right, you can only send binary data to file opened in binary mode. The 
default sys.stdout is in text mode. I am pretty sure that remains true 
even if stdout is redirected. (You did not mention your OS.) You would 
have to open such a file and make sys.stdout point to it.
sys.stdout = my_binary_file.
But why do that? Just open the file and write to it directly without the 
above.

-- 
Terry Jan Reedy

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#21365

On Mar 7, 4:10 pm, Terry Reedy <tjre...@udel.edu> wrote:
> On 3/7/2012 5:35 PM, Peter Kleiweg wrote:
>
>
>
>
>
>
>
>
>
> > Dave Angel schreef op de 7e dag van de lentemaand van het jaar 2012:
>
> >> On 03/07/2012 02:41 PM, Peter Kleiweg wrote:
> >>> I want to write out some binary data to stdout in Python3. I
> >>> thought the way to do this was to call detach on sys.stdout. But
> >>> apparently, you can't. Here is a minimal script:
>
> >>>       #!/usr/bin/env python3.1
> >>>       import sys
> >>>       fp = sys.stdout.detach()
>
> >>> Not yet using fp in any way, this script gives the following error:
>
> >>>       Exception ValueError: 'underlying buffer has been detached' in
>
> >>> Same in Python 3.1.4 and Python 3.2.2
>
> >>> So, what do I do if I want to send binary data to stdout?
>
> >> sys.stdout.write(  some_binary_data )
>
> > TypeError: must be str, not bytes
>
> Right, you can only send binary data to file opened in binary mode. The
> default sys.stdout is in text mode. I am pretty sure that remains true
> even if stdout is redirected. (You did not mention your OS.) You would
> have to open such a file and make sys.stdout point to it.
> sys.stdout = my_binary_file.
> But why do that? Just open the file and write to it directly without the
> above.
>
> --
> Terry Jan Reedy

Write binary data to sys.stdout.buffer.

-Mark

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#21369

Peter Kleiweg <pkleiweg <at> xs4all.nl> writes:
> Not yet using fp in any way, this script gives the following error:
> 
>     Exception ValueError: 'underlying buffer has been detached' in

You're probably using print() or some such which tries to write to sys.stdout.
It's safest to just write to sys.stdout.buffer rather than using detach.

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