[Python-Dev] file system path protocol PEP (original) (raw)

Steven D'Aprano steve at pearwood.info
Fri May 13 06:19:40 EDT 2016

On Thu, May 12, 2016 at 07:22:25PM +0200, Sjoerd Job Postmus wrote:

The whole point of adding os.fspath is to make it easier to use Path objects. This is in an effort to gain greater adoption of pathlib in libraries. Now, this is an excellent idea.

However, if it were to reject bytes, that would mean that when libraries start to use pathlib, it would suddenly become harder for people that actually need bytes-support to use pathlib.

I'm not sure how it would be harder. Currently, if you need bytes paths, you can't use pathlib. That won't change, so it will be exactly as hard as it is now.

Now, the claim 'if you need bytes, you should not be using pathlib` is a reasonable one. But what if I need bytes and a specific library (say, image handling, or a web framework, or ...). It's not up to me if that library uses pathlib or plain old os.path.join.

I feel this is Not Our Problem. Surely the stdlib cannot be held responsible for all the poor decisions made by third-party libraries? If a library hard-codes "\" as their directory separator, because everyone uses Windows, you'd simply say "this library is not very good for my use-case". Likewise if it rejects bytes paths, then:

I don't doubt that all three options are unpleasant, but I don't see how they are the fault of this PEP. This PEP supports Path-Like objects that return bytes paths. Its up to library authors to support bytes paths, or not, as they see fit.

-- Steve

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