[issue24132] Direct sub-classing of pathlib.Path

[qb-cea]

qb-cea  added the comment:

Hi,

Thanks for reviving this! Feel free to reuse any code I wrote in my PR (or the 
whole PR itself), I do not think I will ever get around to finishing this work 
myself.

--

___
Python tracker 
<https://bugs.python.org/issue24132>
___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue24132] Direct sub-classing of pathlib.Path

[qb-cea]

qb-cea <quentin.bou...@cea.fr> added the comment:

> What about AbstractPath instead of _PurePath ?

I will use this, thanks.

--

___
Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue24132>
___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue24132] Direct sub-classing of pathlib.Path

[qb-cea]

qb-cea <quentin.bou...@cea.fr> added the comment:

Hi all,

I made a pull request proposing a fix for this issue. There is still quite a 
lot to be done:
 - I exposed some variables (and probably methods too) that used to be hidden;
 - I did not update the documentation;
 - I did not add a proper test.

I will try to fix those by the end of the week.

The patch mainly consists of two things:
 - having Path (resp. PurePath) be a variable pointing at either 
(Pure)PosixPath or (Pure)WindowsPath, depending on the platform (like Kevin 
Norris suggested);
 - introducing two new abstract classes _PurePath and ConcretePath from which 
PurePosixPath, PureWindowsPath and PosixPath, WindowsPath classes inherit;
 - removing the _Flavor classes, and redistributing their method to 
platform-specific classes.

Ideally I would like _PurePath to become a public class, but I could not come 
up with a proper name. Any feedback is more than welcome =]

--

___
Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue24132>
___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue24132] Direct sub-classing of pathlib.Path

[qb-cea]

Change by qb-cea <quentin.bou...@cea.fr>:


--
keywords: +patch
pull_requests: +5981
stage:  -> patch review

___
Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue24132>
___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue24132] Direct sub-classing of pathlib.Path

[qb-cea]

Change by qb-cea <quentin.bou...@cea.fr>:


--
nosy: +qb-cea

___
Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue24132>
___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue32665] pathlib.Path._from_parsed_parts should call cls.__new__(cls)

[qb-cea]

qb-cea <quentin.bou...@cea.fr> added the comment:

Typo in the code of the previous comment:

- __slots__ = ("new_attr",)
+ __slots__ = ("_new_attr",)

--
type:  -> behavior

___
Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue32665>
___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue32665] pathlib.Path._from_parsed_parts should call cls.__new__(cls)

[qb-cea]

New submission from qb-cea <quentin.bou...@cea.fr>:

Hi,

I tried subclassing pathlib.Path and provide it with a new attribute (basically 
an accessor to an extended attribute). I am rather new to the concept of 
__slots__ and __new__() but here is how I pictured it should look:

from errno import ENODATA
from os import getxattr, setxattr
from pathlib import Path

class Path_(type(Path())):

__slots__ = ("new_attr",)

def __new__(cls, *args, new_attr=None, **kwargs):
self = super().__new__(cls, *args, **kwargs)
self._new_attr = new_attr
return self

@property
def new_attr(self):
if self._new_attr:
return self._new_attr

try:
new_attr = getxattr(self, "user.new_attr")
except OSError as exc:
if exc.errno != ENODATA:
raise exc
else:
self._new_attr = new_attr
return new_attr

new_attr = b"something_dynamic" # for example uuid4().bytes
setxattr(self, "user.new_attr", new_attr)
self._new_attr = new_attr
return new_attr

The issue I have is that although my class defines its own __new__() method, it 
is not always called by the methods of pathlib.Path. For example:

>>> Path_("/etc").parent.new_attr
Traceback (most recent call last):
  File "", line 1, in 
  File "/path/to/reproducer.py", line 19, in new_attr
if self._new_attr:
AttributeError: _new_attr

The current workaround I use consists in redefining pathlib.Path's 
_from_parsed_parts() method in my class: instead of creating a new object using:
object.__new__(cls)
my implementation uses:
cls.__new__(cls)

This is the first time I play with the __new__() special method, so it is 
possible I missed something, if so, sorry for the noise.

------
components: Library (Lib)
files: reproducer.py
messages: 310671
nosy: pitrou, qb-cea
priority: normal
severity: normal
status: open
title: pathlib.Path._from_parsed_parts should call cls.__new__(cls)
versions: Python 3.6
Added file: https://bugs.python.org/file47409/reproducer.py

___
Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue32665>
___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com