Nick Coghlan writes: > On 15 April 2016 at 00:52, Stephen J. Turnbull <[email protected]> wrote: > > Nick Coghlan writes: > > > > > The use case for returning bytes from __fspath__ is DirEntry, so you > > > can write things like this in low level code: > > > > > > def myscandir(dirpath): > > > for entry in os.scandir(dirpath): > > > if entry.is_file(): > > > with open(entry) as f: > > > # do something > > > > Excuse me, but that is *not* a use case for returning bytes from > > DirEntry.__fspath__. open() is perfectly happy taking str (including > > surrogate-encoded rawbytes). > > That results in a different type for the file object's name: > > >>> open("README.md").name > 'README.md' > >>> open(b"README.md").name > b'README.md'
OK, you win, __fspath__ needs to be polymorphic. But you've just shifted me to -1 on "os.fspath": it's an attractive nuisance. EIBTI, applications and high-level library functions should use os.fsdecode or os.fsencode. Functions that take a polymorphic argument and want preserve type should invoke __fspath__ on the argument. That will visually signal that the caller is not merely low-level, but is explicitly a boundary function. (You could rename the generic function as "os._fspath", I guess, but I *really* want to deprecate calling the polymorphic version in user code. _fspath can be added if experience shows that polymorphic usage is very desireable outside the stdlib. This remark is in my not-so-Dutch opinion, of course.) > The guarantee we want to provide those folks is that if they're > operating in the binary domain they'll stay there. Et tu, Nick? "Guarantee"?! You can't guarantee any such thing with an implicitly invoked polymorphic API like this one -- unless you consider a crashed program to be in the binary domain. ;-) Note that the current proposala don't even do that for the binary domain, only for the text domain! _______________________________________________ Python-Dev mailing list [email protected] https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com