[Python-Dev] [Python-3000] New proposition for Python3 bytes filename issue

["Martin v. Löwis"]

Guido van Rossum wrote:
> However
> the *proposed* behavior (returns bytes if the arg was bytes, and
> returns str when the arg was str) is IMO sane, and no different than
> the polymorphism found in len() or many builtin operations.

My concern still is that it brings the bytes type into the status of
another character string type, which is really bad, and will require
further modifications to Python for the lifetime of 3.x.

This is because applications will then regularly use byte strings for
file names on Unix, and regular strings on Windows, and then expect
the program to work the same without further modifications. The next
question then will be environment variables and command line arguments,
for which we then should provide two versions (e.g. sys.argv and
sys.argvb; for os.environ, os.environ["PATH"] could mean something
different from os.environ[b"PATH"]). And so on (passwd/group file,
Tkinter, ...)

Regards,
Martin