[Python-Dev] Using environment variables problematic for embedded python.

[Guido van Rossum]

This seems more fit for the tracker; can you file there? (Then post the
issue link here.) I do think you have a legitimate use case to set the
default encoding to utf-8. (Though there may be a way already.) Does Python
3.3 have te same bug?

On Wednesday, October 3, 2012, Campbell Barton wrote:

> On Thu, Oct 4, 2012 at 1:35 PM, Campbell Barton <ideasman42 at gmail.com<javascript:;>>
> wrote:
> > Hi,
> >
> > We've run into an issue recently with blender3d on ms-windows where we
> > want to enforce the encoding is UTF-8 with the embedded python
> > interpreter.
> > (the encoding defaults to cp437).
> >
> > I naively thought setting the environment variable before calling
> > Py_Initialize() would work, but the way python DLL loads, it gets its
> > own environment variables that cant be modified directly [1].
> > eg, _putenv("PYTHONIOENCODING=utf-8:surrogateescape");
> >
> > We had bug reports by windows users not able to export files because
> > the stdout errors on printing paths with unsupported encoding. [2],[3]
> >
> > ---
> >
> > Of course we could distribute blender with a bat file launcher that
> > sets env variables, or ask the user to set their env variable - but I
> > dont think this is really a good option.
> >
> > I tried overriding the stderr & stdout, but this caused another bug in
> > a part of out code that catches exception messages from the stderr.
> > [4]
> > import sys, io
> > sys.stdout = io.TextIOWrapper(sys.stdout.buffer, encoding='utf-8',
> > errors='surrogateescape', line_buffering=True)
> > sys.stderr = io.TextIOWrapper(sys.stderr.buffer, encoding='utf-8',
> > errors='surrogateescape', line_buffering=True)
> >
> >
> >
> > IMHO either of these solutions would be fine.
> >
> > * have a PyOS_PutEnv() function, gettext has gettext_putenv() to
> > workaround this problem.
> >
> > * manage this the same as Py_GetPythonHome(), which can be defined by
> > the embedding application to override the default.
> >
> >
> > Id like to know if there is some known solution to workaround this
> > issue, if not - would either of these would be acceptable in python
> > (can write up a patch if it helps)
> >
> > Regards,
> > Campbell
> >
> > ---
> >
> > [1]
> http://stackoverflow.com/questions/5153547/environment-variables-are-different-for-dll-than-exe
> > [2] http://projects.blender.org/tracker/index.php?func=detail&aid=32750
> > [3] http://projects.blender.org/tracker/index.php?func=detail&aid=31555
> > [4] http://projects.blender.org/tracker/?func=detail&aid=32720
>
> To follow up and give a correction to overwriting sys.stdout/stderr,
> The issue seemed to be that __stderr__/__stdout__ was later
> overwritten, loosing the original reference to the buffer (maybe
> refcount issue here?), either way it would silence the output.
>
>
> import sys, io
> sys.__stdout__ = sys.stdout =
> io.TextIOWrapper(io.open(sys.stdout.fileno(), "wb", -1),
> encoding='utf-8', errors='surrogateescape', newline="\n",
> line_buffering=True)
> sys.__stderr__ = sys.stderr =
> io.TextIOWrapper(io.open(sys.stderr.fileno(), "wb", -1),
> encoding='utf-8', errors='surrogateescape', newline="\n",
> line_buffering=True)
>
> This all works as expected without bug [4] (above), however on exit I
> get an assert in MSVCR90.DLL's write.c (called from python32_d.dll):
> _VALIDATE_CLEAR_OSSERR_RETURN((_osfile(fh) & FOPEN), EBADF, -1);
>
> I'd rather not loose more time debugging why this assert happens,
> IMHO this is too low-level a way to change the encoing of stdio/stderr
> and error-prone too, so some way to reliably set PYTHONIOENCODING from
> a program embedding python is still needed.
>
> --
> - Campbell
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-- 
--Guido van Rossum (python.org/~guido)
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