[Python-Dev] file system path protocol PEP

[Nick Coghlan]

On 12 May 2016 at 02:43, Brett Cannon <brett at python.org> wrote:
> **deep, calming breath**
>
> Here is the PEP for __fspath__(). The draft lives at
> https://github.com/brettcannon/path-pep so feel free to send me PRs for
> spelling mistakes, grammatical errors, etc.

Thanks for putting this together :)

> C API
> '''''
>
> The C API will gain an equivalent function to ``os.fspath()`` that
> also allows bytes objects through::
>
>     /*
>         Return the file system path of the object.
>
>         If the object is str or bytes, then allow it to pass through with
>         an incremented refcount. All other types raise a TypeError.
>     */
>     PyObject *
>     PyOS_RawFSPath(PyObject *path)
>     {
>         if (PyObject_HasAttrString(path, "__fspath__")) {
>             path = PyObject_CallMethodObjArgs(path, "__fspath__", NULL);
>             if (path == NULL) {
>                 return NULL;
>             }
>         }
>         else {
>             Py_INCREF(path);
>         }
>
>         if (!PyUnicode_Check(path) && !PyBytes_Check(path)) {
>             Py_DECREF(path);
>             return PyErr_Format(PyExc_TypeError,
>                                 "expected a string, bytes, or path object,
> not %S",
>                                 path->ob_type);
>         }
>
>         return path;
> }

I'd still like to see this exposed to Python code as os._raw_fspath()
(with the leading underscore just meaning "this probably isn't the API
you want" rather than indicating a private or unstable API), and then
fspath() defined as a wrapper around it which disallows bytes as
output.

However, I don't have a specific use case, and it would be
straightforward to add later, so the overall PEP gets a +1 from me.

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia