[issue5996] abstract class instantiable when subclassing dict

R. David Murray added the comment: Closed issue 31127 as a duplicate of this one. -- nosy: +Kevin Shweh ___ Python tracker ___ ___ Pyth

[issue5996] abstract class instantiable when subclassing dict

R. David Murray added the comment: My apologies, I added Nathaniel to nosy here when I closed the duplicate, but forgot to add a link to the closed issue: issue 28537. -- nosy: +r.david.murray ___ Python tracker __

[issue5996] abstract class instantiable when subclassing dict

Guido van Rossum added the comment: Oh sorry. I received the emails in a strange order. I guess it can stay open. -- resolution: wont fix -> status: closed -> open ___ Python tracker ___

[issue5996] abstract class instantiable when subclassing dict

Guido van Rossum added the comment: Where did you report that? I don't see your name on this bug -- it has a patch that's been unapplied for 5 years, so I doubt it's very important. -- ___ Python tracker __

[issue5996] abstract class instantiable when subclassing dict

Nathaniel Manista added the comment: Wait, really? My report came out of a real bug that I had in my system and shipped to my users; it wasn't academic or contrived at all. -- ___ Python tracker ___

[issue5996] abstract class instantiable when subclassing dict

Guido van Rossum added the comment: Honestly let's just forget about this. -- resolution: -> wont fix status: open -> closed ___ Python tracker ___ __

[issue5996] abstract class instantiable when subclassing dict

Changes by R. David Murray : -- nosy: +Nathaniel Manista, aleax, cvrebert ___ Python tracker ___ ___ Python-bugs-list mailing list Unsu

[issue5996] abstract class instantiable when subclassing dict

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[issue5996] abstract class instantiable when subclassing dict

Xiang Zhang added the comment: I think subclassing builtin types and making it abstract is rare. And when there is a need, we can mimic this in application level (this may also apply to types having custom __new__): In [2]: class CustomDict(dict, metaclass=abc.ABCMeta): ...: def __new__

[issue5996] abstract class instantiable when subclassing dict

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[issue5996] abstract class instantiable when subclassing dict

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[issue5996] abstract class instantiable when subclassing dict

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[issue5996] abstract class instantiable when subclassing dict

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[issue5996] abstract class instantiable when subclassing dict

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[issue5996] abstract class instantiable when subclassing dict

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[issue5996] abstract class instantiable when subclassing dict

Eugene Toder added the comment: They are, when there's a most specific metaclass -- the one which is a subclass of all others (described here http://www.python.org/download/releases/2.2.3/descrintro/#metaclasses, implemented here http://hg.python.org/cpython/file/ab162f925761/Objects/typeobj

[issue5996] abstract class instantiable when subclassing dict

Raymond Hettinger added the comment: IIRC, classes weren't supposed to be able inherit from two classes that had different metaclasses (since differing metaclasses don't necessarily play well with one another). -- nosy: +rhettinger ___ Python track

[issue5996] abstract class instantiable when subclassing dict

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[issue5996] abstract class instantiable when subclassing dict

Eugene Toder added the comment: Anyone has any thoughts on this? -- ___ Python tracker ___ ___ Python-bugs-list mailing list Unsubscri

[issue5996] abstract class instantiable when subclassing dict

Eugene Toder added the comment: This patch fixes the problem by moving the check from object_new to PyType_GenericAlloc. The check is very cheap, so this should not be an issue. -- keywords: +patch nosy: +eltoder Added file: http://bugs.python.org/file21600/abc.patch _

[issue5996] abstract class instantiable when subclassing dict

Changes by Éric Araujo : -- nosy: +eric.araujo versions: +Python 3.3 -Python 2.6 ___ Python tracker ___ ___ Python-bugs-list mailing li

[issue5996] abstract class instantiable when subclassing dict

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[issue5996] abstract class instantiable when subclassing dict

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[issue5996] abstract class instantiable when subclassing dict

Daniel Urban added the comment: I think, that the reason is that, object.__new__ checks, if the class is instantiable (object_new in Objects/typeobject.c ). dict.__new__ (and tuple.__new__, and I guess the __new__ method of other built-in types) doesn't call object.__new__, but user defined t

[issue5996] abstract class instantiable when subclassing dict

Terry J. Reedy added the comment: I presume you claim the dict example to be a bug in relation to "A class that has a metaclass derived from ABCMeta cannot be instantiated unless all of its abstract methods and properties are overridden." There is the same difference with @abstractproperty Wind

[issue5996] abstract class instantiable when subclassing dict

Antoine Pitrou added the comment: Also happens with other builtin types such as tuple. It's probably related to the way subclasses of those types are instantiated, bypassing the normal metaclass mechanism. -- nosy: +pitrou priority: -> normal versions: +Python 2.7, Python 3.1, Python 3

[issue5996] abstract class instantiable when subclassing dict

New submission from johannes raggam : when declaring a abstract base class with an abstract property or method and subclassing from dict, the class is instantiable (instanceable?). >>> import abc >>> class A(object): ... __metaclass__ = abc.ABCMeta ... @abc.abstractproperty ... def a