sys.stdout.detach() results in ValueError

[Peter Kleiweg]

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?

 

[Dave Angel]

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.

 

[Peter Kleiweg]

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

sys.stdout.write( some_binary_data )

TypeError: must be str, not bytes

 

[Terry Reedy]

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


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.

 

[Mark Tolonen]

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.

Write binary data to sys.stdout.buffer.

-Mark

 

[Benjamin Peterson]

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.