> >> Think of e.g. embedded Python interpreters or py2exe-style applications
> >> running on Linux or other systems that don't use Unicode APIs 
> >> for FS-interaction or have fixed FS-encodings.
> > 
> > What is the problem here? Python does guess the filesystem encoding. If the encoding is "wrong" (not the value expected by the user), filenames are not displayed correctly (mojibake) but it does just work. Anyway, why is it not possible to use PYTHONFSENCODING here? Are you talking to Python modules loaded from a non-ascii path?
> > 
> > Sorry, but I do not understand.
> 
> In such environments you cannot expect the user to configure the
> system properly (i.e. set an environment variable). Instead, the
> application has to provide an educated guess to the Python
> interpreter in some way, hence the idea to use a configuration
> file or perhaps provide a C API that can be used to set the
> variable before initializing the interpreter.

Why wouldn't the embedding application just set the environment var
before initializing the Python interpreter?