[Python-3000] Path Reform: Get the ball rolling

[Greg Ewing]

Mike Orr wrote:
> Perhaps this
> disrecommendation should be lifted, especially since both Mac and
> Windows do the right thing with "/", "..", and "." now.

Is anyone still supporting VMS? It has a wildly
different pathname syntax.

In any case, if we all start writing code that
makes assumptions about pathname syntax, and
some platform comes along in the future that
does things differently, we're hosed. Do we
want to take that risk?

> The other thing is, ".." and "." seem to be smarter than
> os.path.dirname.

You can certainly get different results if you
interpret a path containing . or .. through the
file system than if you treat it as a pure
pathname manipulation. But the same will be
true of any OO replacement that also restricts
itself to pathname manipulation -- it won't be
able to treat . and .. any more smartly than
os.path does.

> '.' off a file chops the filename component, 

Not sure what you mean by that. On Unix, if you
try to open "foo.c/." where "foo.c" is not a
directory, you get an exception:

    >>> open("foo.c/.")
    Traceback (most recent call last):
      File "<stdin>", line 1, in ?
    IOError: [Errno 20] Not a directory: 'foo.c/.'

But os.path has no idea what foo.c is, so it
just treats joining "." to a path and then
normalising as a no-op.

> '..' off a file goes to the file's directory, while '..' off
> a directory goes to the directory's parent.

These aren't different things -- in both cases
you're getting the directory that contains the
object in question.

 > I think a method like .ancestor(N) would be useful,
> meaning "do '..' N times.

That would be handy, yes.

--
Greg