[Python-ideas] changing sys.stdout encoding

Nathan Schneider nathan at cmu.edu
Fri Jun 8 02:59:31 CEST 2012

On Thu, Jun 7, 2012 at 5:14 PM, Rurpy <rurpy at yahoo.com> wrote:
> On 06/07/2012 03:45 PM, Nick Coghlan wrote:
>> The interpreter uses the standard streams internally, and
>> they're one of the first things created during interpreter
>> startup. User provided code doesn't start running until well
>> after they're initialised.
> In other words, the stream objects referenced by sys.std*
> are opened before the user code runs?
> But if there are no operations on those streams until my
> user code runs, they are still in the same state they were
> after they were initialized, yes?
> So if one wanted to provide an "only before first use"
> set_encoding() function, why couldn't that function reexecute
> the codecs part of the initialization code a second time?
> Of course there would need to be some sort of flag that it
> could use to verify the stream was still in its initial state.
>> If user level code doesn't want those streams, it needs to
>> replace them with something else.
> Yes, this is what the code I googled up does:
>  import codecs
>  sys.stdout = codecs.getwriter(opts.encoding)(sys.stdout.buffer)

What if codecs contained convenience methods for stdin and stdout?
I.e. the above could be written more simply as

  import codecs

This is much more memorable than the current option, and would also
make life easier when working with fileinput (whose openhook argument
can be set to control encoding of input *file* streams, but when it
falls back to stdin this preference is ignored).

> But that code is not obvious to someone who has been able to do
> all his encoded IO (with the exception of sys.stdout) using just
> the encoding parameter of open().  Hence my question if some-
> thing like a set_encoding() method/function that would work on
> sys.stdout is feasible.  I don't see an answer to that in your
> statement above.
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