[issue41109] subclasses of pathlib.PurePosixPath never call __init__ or __new__
Louis-Vincent Boudreault added the comment: This is not true, because the classmethod used the library shortcuts the class mro order, this is to prevent infinite loop inthe __new__. However, If it was using __init__ before hand, we would Not have this issue Le jeu. 13 août 2020 à 15:31, Louis-Vincent Boudreault < lv.boudreaul...@gmail.com> a écrit : > This is not true, because the classmethod use the library shortcuts the > class mro order, to prevent infinite loop inthe __new__. However, it was > using __init__ before hand, we would > Not have this issue > > > Le jeu. 13 août 2020 à 15:27, Jeffrey Kintscher > a écrit : > >> >> Jeffrey Kintscher added the comment: >> >> Adding __init__() to PurePath complicates things and doesn't provide any >> benefit. A subclass that calls super.__init__() ends up invoking >> object.__init__(), which is perfectly fine. >> >> I was able to find a solution by calling type(self)() instead of >> object.__new__() in most cases. I am working on a PR. >> >> -- >> >> ___ >> Python tracker >> <https://bugs.python.org/issue41109> >> ___ >> > -- ___ Python tracker <https://bugs.python.org/issue41109> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue41109] subclasses of pathlib.PurePosixPath never call __init__ or __new__
Louis-Vincent Boudreault added the comment: This is not true, because the classmethod use the library shortcuts the class mro order, to prevent infinite loop inthe __new__. However, it was using __init__ before hand, we would Not have this issue Le jeu. 13 août 2020 à 15:27, Jeffrey Kintscher a écrit : > > Jeffrey Kintscher added the comment: > > Adding __init__() to PurePath complicates things and doesn't provide any > benefit. A subclass that calls super.__init__() ends up invoking > object.__init__(), which is perfectly fine. > > I was able to find a solution by calling type(self)() instead of > object.__new__() in most cases. I am working on a PR. > > -- > > ___ > Python tracker > <https://bugs.python.org/issue41109> > ___ > -- ___ Python tracker <https://bugs.python.org/issue41109> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue41109] subclasses of pathlib.PurePosixPath never call __init__ or __new__
Louis-Vincent Boudreault added the comment:
Path.__new__ should not call _from_parts because it breaks the specialization
by directly using object.__new__.
This is why `_from_parts` has to be duplicated in each subclass's `__new__`.
My suggestion (first draft) is to do the parsing of arguments inside an
`__init__` in the Path class hierarchy
and deprecate `_from_parts`.
```
class PurePath:
def __new__(cls, *args):
if cls is PurePath:
cls = PureWindowsPath if os.name == 'nt' else PurePosixPath
super().__new__(cls, *args) # Here we remove call to from_parts
def __init__(self, *args):
# We should have an __init__ in the hierarchy.
drv, root, parts = self._parse_args(args) # this would get the proper
_flavour.
self._drv = drv
self._root = root
self._parts = parts
...
class Path(PurePath):
def __new__(cls, *args, **kwargs):
if cls is Path:
cls = WindowsPath if os.name == 'nt' else PosixPath
# REMOVE THIS LINE: self = cls._from_parts(args, init=False) #
if not self._flavour.is_supported:
raise NotImplementedError("cannot instantiate %r on your system"
% (cls.__name__,))
return super().__new__(cls, *args, **kwargs) # Use super
```
I don't know what is the purpose of `_init` and if it could be replaced by an
extra keyword argument in __init__.
The class method `_from_parts` would become deprecated since the argument
parsing would be now handled by `__init__`.
By using __init__ and avoid the direct call to `object.__new__` we would
respect class specialization and custom class could be implemented intuitively.
--
nosy: +louis-vincent.boudre
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