Description

JelleZijlstra

opened on Mar 18, 2017

Issue body actions

BPO	29847
Nosy	@brettcannon, @pitrou, @serhiy-storchaka, @jstasiak, @JelleZijlstra, @DimitrisJim, @remilapeyre, @uriyyo
PRs	bpo-29847: Path subclasses raise TypeError given kwargs #13399 gh-74033: Fix bug when Path takes and ignores **kwargs #19632

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2017-03-18.15:22:47.434>
labels = ['type-bug', '3.8', '3.9', '3.10', '3.7', 'library']
title = 'Path takes and ignores **kwargs'
updated_at = <Date 2020-06-10.22:05:47.572>
user = 'https://github.com/JelleZijlstra'

bugs.python.org fields:

activity = <Date 2020-06-10.22:05:47.572>
actor = 'remi.lapeyre'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2017-03-18.15:22:47.434>
creator = 'JelleZijlstra'
dependencies = []
files = []
hgrepos = []
issue_num = 29847
keywords = ['patch']
message_count = 9.0
messages = ['289817', '289896', '289897', '289902', '289944', '289945', '289946', '289998', '369520']
nosy_count = 8.0
nosy_names = ['brett.cannon', 'pitrou', 'serhiy.storchaka', 'jstasiak', 'JelleZijlstra', 'Jim Fasarakis-Hilliard', 'remi.lapeyre', 'uriyyo']
pr_nums = ['13399', '19632']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue29847'
versions = ['Python 3.7', 'Python 3.8', 'Python 3.9', 'Python 3.10']

Linked PRs

• GH-74033: Drop deprecated pathlib.Path keyword arguments #118793

Activity

1. JelleZijlstra commented on Mar 18, 2017

   

   JelleZijlstra

   on Mar 18, 2017

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   pathlib.Path.__new__ takes **kwargs, but doesn't do anything with them (https://github.com/python/cpython/blob/master/Lib/pathlib.py#L979). This doesn't appear to be documented.

   This feature should presumably be either documented or removed (probably removed unless I'm missing some reason for having it).

   Brief discussion on a typeshed PR at python/typeshed#991 (diff)
2. brettcannon commented on Mar 20, 2017

   

   brettcannon

   on Mar 20, 2017

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   Yep, kwargs should be dropped since it isn't used or documented: https://docs.python.org/3/library/pathlib.html#pathlib.PurePath (probably just a hold-over from when it did in some earlier version of the code).
3. brettcannon

   added

   stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

   3.7 (EOL)end of lifeend of life

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on Mar 20, 2017
4. JelleZijlstra commented on Mar 20, 2017

   

   JelleZijlstra

   on Mar 20, 2017

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   Thanks, I'll add a PR. This doesn't need to be documented, right?
5. serhiy-storchaka commented on Mar 20, 2017

   

   serhiy-storchaka

   on Mar 20, 2017

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   The support of **kwargs in Path.__new__ is needed if you want to implement a subclass of Path with __init__ accepting keyword arguments (and since Path constructor takes variable number of positional arguments, new arguments should be keyword-only).

   >>> import pathlib
   >>> class MyPath(pathlib.PosixPath):
   ...     def __init__(self, *args, spam=False):
   ...         self.spam = spam
   ... 
   >>> p = MyPath('/', spam=True)
   >>> p
   MyPath('/')
   >>> p.spam
   True

   Removing **kwargs from Path.__new__ will break the above example.

   >>> MyPath('/', spam=True)
   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
   TypeError: __new__() got an unexpected keyword argument 'spam'
6. brettcannon commented on Mar 21, 2017

   

   brettcannon

   on Mar 21, 2017

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   Shoot, that's too bad. I guess we should document it then so people are aware that keyword arguments are ignored, else we will break subclasses. There's also an unfortunate difference between PurePath and Path as PurePath doesn't have this quirk.
7. serhiy-storchaka commented on Mar 21, 2017

   

   serhiy-storchaka

   on Mar 21, 2017

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   I don't know whether it was the intension of Antoine or just an oversight. I don't know whether it is used in the wild. But we can at least raise a TypeError for concrete classes PosixPath and WindowsPath if ignoring keyword arguments is a problem. Many extension types don't take keyword arguments, but their subclasses accept and ignore keyword arguments. For example:

   >>> filter(None, [], foo=123)
   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
   TypeError: filter() does not take keyword arguments
   >>> class X(filter): pass
   ... 
   >>> X(None, [], foo=123)
   <__main__.X object at 0xb6fdcacc>
8. pitrou commented on Mar 21, 2017

   

   pitrou

   on Mar 21, 2017

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   The support of **kwargs in Path.__new__ is needed if you want to implement a subclass of Path with __init__ accepting keyword arguments

   I don't remember exactly, but I think this was the intention indeed. There was originally an openat-using subclass, and IIRC it took additional parameters (such as the directory fd). That got scrapped quite early in the process, so we can remove the **kwargs thing now.
9. brettcannon commented on Mar 22, 2017

   

   brettcannon

   on Mar 22, 2017

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   Then I vote for Serhiy's idea of simply raising an exception in the concrete subclasses when a keyword argument is given.
10. remilapeyre commented on May 21, 2020

    

    remilapeyremannequin

    on May 21, 2020

    Mannequin

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    PurePath subclasses cannot support kwargs as __new__() does not accept **kwargs:

    >>> from pathlib import PurePath
    >>> class MyPurePath(PurePath):
    ...     def __init__(self, *args, **kargs): pass
    ... 
    >>> MyPurePath('foo', spam=True)
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    TypeError: __new__() got an unexpected keyword argument 'spam'

    The behaviour for this should probably be made the same for both Path and PurePath.
11. remilapeyre

    added

    3.8 (EOL)end of lifeend of life

    3.9 (EOL)end of lifeend of life

    3.10 (EOL)end of lifeend of life

    on Jun 10, 2020
12. ezio-melotti

    transferred this issue fromon Apr 10, 2022
13. jaraco commented on Oct 10, 2022

    

    jaraco

    on Oct 10, 2022

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    As reported in the dupe bug, this bug led to masking a user mistake.
14. brettcannon

    added

    topic-pathlib

    on Oct 14, 2022
15. barneygale commented on Jan 5, 2023

    

    barneygale

    on Jan 5, 2023

    Contributor

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    #100481 would fix this without breaking subclassing by adding an __init__() method.
16. miss-islington

    added a commit that references this issue on Jan 14, 2023

    gh-74033: Fix bug when Path takes and ignores **kwargs (GH-19632)

    080cb27
17. brettcannon commented on Jan 14, 2023

    

    brettcannon

    on Jan 14, 2023

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    I took #19632 as a fix, but it can obviously be tweaked as long as the deprecation warning sticks around.
18. brettcannon

    closed this as completedon Jan 14, 2023
19. barneygale

    added 5 commits that reference this issue on May 8, 2024

    pythonGH-74033: Drop deprecated `pathlib.Path()` keyword arguments

    2468f33

    Merge branch 'main' into pythongh-74033-remove

    85eb732

    Merge branch 'main' into pythongh-74033-remove

    92cbfd0

    Merge branch 'main' into pythongh-74033-remove

    36bb885

    GH-74033: Drop deprecated `pathlib.Path` keyword arguments (#118793)

    7d8725a
20. estyxx

    added a commit that references this issue on Jul 17, 2024

    pythonGH-74033: Drop deprecated `pathlib.Path` keyword arguments (pyt…

    3fee9e3

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