On 10 April 2016 at 15:58, Greg Ewing <greg.ew...@canterbury.ac.nz> wrote:
> Brett Cannon wrote:
>
>> Depends if you use `/` or `\` as your path separator
>
>
> Or whether your pathnames look entirely different, e.g VMS:
>
> device:[topdir.subdir.subsubdir]filename.ext;version
>
> Pathnames are very much OS-dependent in both syntax *and* semantics.
>
> Even the main two in use today (unix and windows) can't be
> mapped directly onto each other, because windows has drive
> letters and unix doesn't.
This does raise a concrete API design question: how should
PurePath.__fspath__ behave when called on a mismatched OS?
For PurePath vs Path, the latter raises NotImplementedError if you try
to create a concrete path that doesn't match the running system:
>>> pathlib.PureWindowsPath(".")
PureWindowsPath('.')
>>> pathlib.WindowsPath(".")
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib64/python3.4/pathlib.py", line 910, in __new__
% (cls.__name__,))
NotImplementedError: cannot instantiate 'WindowsPath' on your system
The question we need to address is what happens if you do:
>>> os.fspath(pathlib.PureWindowsPath("."))
on a *nix system?
Similar to my proposal for dealing with DirEntry.path being a
bytes-like object, I'd like to suggest raising TypeError in __fspath__
if the request is nonsensical for the currently running system - *nix
systems can *manipulate* Windows paths (and vice-versa), but actually
trying to *use* them with the local filesystem isn't going to work
properly, since the syntax and semantics are different.
>>> os.fspath(pathlib.WindowsPath("."))
Traceback (most recent call last):
...
TypeError: cannot render 'PureWindowsPath' as filesystem path on
'posix' system
(I'm also suggesting replacing "your" with the value of os.name)
Cheers,
Nick.
--
Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia
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