[Python-Dev] The path module PEP (original) (raw)

Gustavo J. A. M. Carneiro gjc at inescporto.pt
Thu Jan 26 13:03:28 CET 2006

On Wed, 2006-01-25 at 22:35 -0600, Ian Bicking wrote:

Gustavo J. A. M. Carneiro wrote: > On a slightly different subject, regarding path / path, I think it > feels much more natural path + path. Path.join is really just a string > concatenation, except that it adds a path separator in the middle if > necessary, if I'm not mistaken.

No, it isn't, which maybe is why / is bad. os.path.join(a, b) basically returns the path as though b is interpreted to be relative to a. I.e.,

os.path.join('/foo', '/bar') == '/bar'. Not much like concatenation at all.

Really? This is not like the unix command line. At least in Linux, /foo/bar is the same as /foo//bar and /foo///bar, etc. But I admit it can be useful in some cases.

Plus string concatenation is quite useful with paths, e.g., to add an extension.

I see your point. Although perhaps adding an extension to a file should be the exception and not the rule, since adding extensions is rarely used compared to joining paths? Maybe Path.add_extension() ?

BTW, regarding Path subclassing basestr, there exists "prior art" for this Path thing in SCons. In SCons, we (users, I'm not a scons dev) have to constantly deal with Node instances. Most scons functions that accept Nodes also accept strings, but a Node is not a string. When calling an os function with Nodes, one has to convert it to string first, using str(). IMHO, having to decorate Node instances with str() sometimes is no big deal, really. And, given enough time, perhaps most of the python standard library could be enhanced to accept Path instances in addition to C strings.

If a URI class implemented the same methods, it would be something of a question whether uri.joinpath('/foo/bar', 'baz') would return '/foo/baz' (and urlparse.urljoin would) or '/foo/bar/baz' (as os.path.join does). I assume it would be be the latter, and urljoin would be a different method, maybe something novel like "urljoin".

I honestly don't understand the usefulness of join('/foo/bar', 'baz') ever returning '/foo/baz' instead of '/foo/bar/baz'. How would the former be of any use? If it has no use, then please don't complicate things even more :)

Regards.

-- Gustavo J. A. M. Carneiro <gjc at inescporto.pt> <gustavo at users.sourceforge.net> The universe is always one step beyond logic.

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