[issue14617] confusing docs with regard to __hash__
Raymond Hettinger added the comment: This can wait until after the release. We will have periodic point releases where further doc updates can go in. -- nosy: +rhettinger ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14617 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14617] confusing docs with regard to __hash__
Ethan Furman added the comment: RC2 has just been released. Any chance of this getting in to the final release? Nobobdy has pointed out any problems with the last update... -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14617 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14617] confusing docs with regard to __hash__
Roundup Robot added the comment: New changeset 957e1eef3296 by R David Murray in branch '3.2': #14617: clarify discussion of interrelationship of __eq__ and __hash__. http://hg.python.org/cpython/rev/957e1eef3296 New changeset c8d60d0c736b by R David Murray in branch 'default': Merge #14617: clarify discussion of interrelationship of __eq__ and __hash__. http://hg.python.org/cpython/rev/c8d60d0c736b -- nosy: +python-dev ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14617 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14617] confusing docs with regard to __hash__
R. David Murray added the comment: I rewrote the section a bit differently than you did in your patch...if you think my changes are not an improvement please let me know. -- nosy: +r.david.murray resolution: - fixed stage: - committed/rejected status: open - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14617 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14617] confusing docs with regard to __hash__
Ethan Furman added the comment: R. David Murray wrote: I rewrote the section a bit differently than you did in your patch...if you think my changes are not an improvement please let me know. This line is incorrect: A class which defines its own :meth:`__hash__` that explicitly raises a :exc:`TypeError` would be incorrectly identified as hashable by an ``isinstance(obj, collections.Hashable)`` call. It should be would not be correctly identified as hashable. Otherwise, looks great. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14617 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14617] confusing docs with regard to __hash__
Ethan Furman added the comment: Ethan Furman wrote: Ethan Furman added the comment: R. David Murray wrote: I rewrote the section a bit differently than you did in your patch...if you think my changes are not an improvement please let me know. This line is incorrect: A class which defines its own :meth:`__hash__` that explicitly raises a :exc:`TypeError` would be incorrectly identified as hashable by an ``isinstance(obj, collections.Hashable)`` call. It should be would not be correctly identified as hashable. Otherwise, looks great. Argh. Nevermind! It all looks good. :) -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14617 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14617] confusing docs with regard to __hash__
Ethan Furman added the comment: Any problems with the current doc patch? If not, can it be applied before RC1? -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14617 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14617] confusing docs with regard to __hash__
Changes by Antoine Pitrou pit...@free.fr: -- nosy: +ncoghlan ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14617 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14617] confusing docs with regard to __hash__
Ethan Furman et...@stoneleaf.us added the comment: Newest changes uploaded. -- Added file: http://bugs.python.org/file25707/__hash__3.diff ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14617 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14617] confusing docs with regard to __hash__
Changes by Chris Rebert pyb...@rebertia.com: -- nosy: +cvrebert ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14617 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14617] confusing docs with regard to __hash__
Ethan Furman et...@stoneleaf.us added the comment: Are the changes good? Can they be commited? -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14617 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14617] confusing docs with regard to __hash__
Changes by Arfrever Frehtes Taifersar Arahesis arfrever@gmail.com: -- nosy: +Arfrever ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14617 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14617] confusing docs with regard to __hash__
New submission from Ethan Furman et...@stoneleaf.us: From http://docs.python.org/py3k/reference/datamodel.html#object.__hash__ --- Classes which inherit a __hash__() method from a parent class but change the meaning of __eq__() such that the hash value returned is no longer appropriate (e.g. by switching to a value-based concept of equality instead of the default identity based equality) can explicitly flag themselves as being unhashable by setting __hash__ = None in the class definition. Doing so means that not only will instances of the class raise an appropriate TypeError when a program attempts to retrieve their hash value, but they will also be correctly identified as unhashable when checking isinstance(obj, collections.Hashable) (unlike classes which define their own __hash__() to explicitly raise TypeError). If a class that overrides __eq__() needs to retain the implementation of __hash__() from a parent class, the interpreter must be told this explicitly by setting __hash__ = ParentClass.__hash__. Otherwise the inheritance of __hash__() will be blocked, just as if __hash__ had been explicitly set to None. --- The first paragraph says the user has to change __hash__ if it's different because of changes to __eq__, the second paragraph says __hash__ is automatically removed if __eq__ is changed; the second paragraph reflects reality. Proposed change: --- Classes which change the meaning of __eq__() (thus losing automatic delegation to the parent class' __hash__) can explicitly flag themselves as being unhashable by setting __hash__ = None in the class definition (which is otherwise done implicity). Having __hash__ set to None, either explicitly or implicitly, means that not only will instances of the class raise an appropriate TypeError when a program attempts to retrieve their hash value, but they will also be correctly identified as unhashable when checking isinstance(obj, collections.Hashable) (unlike classes which define their own __hash__() to explicitly raise TypeError). If a class that overrides __eq__() needs to retain the implementation of __hash__() from a parent class, the interpreter must be told this explicitly by setting __hash__ = ParentClass.__hash__. --- Patch attached. -- assignee: docs@python components: Documentation, Interpreter Core files: __hash__.diff keywords: patch messages: 158644 nosy: docs@python, stoneleaf priority: normal severity: normal status: open title: confusing docs with regard to __hash__ type: behavior versions: Python 3.1, Python 3.2, Python 3.3 Added file: http://bugs.python.org/file25261/__hash__.diff ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14617 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14617] confusing docs with regard to __hash__
Changes by Éric Araujo mer...@netwok.org: -- versions: +Python 2.7 -Python 3.1 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14617 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14617] confusing docs with regard to __hash__
Éric Araujo mer...@netwok.org added the comment: Some of the sentence phrasing still sounds a bit awkward to me (“[...], means that not only will instances” for example, and I would also remove the parens at the end), but globally I think this is an improvement. -- nosy: +eric.araujo ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14617 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14617] confusing docs with regard to __hash__
Ethan Furman et...@stoneleaf.us added the comment: Éric Araujo wrote: Changes by Éric Araujo mer...@netwok.org: -- versions: +Python 2.7 -Python 3.1 The docs for 2.7 are correct, as __hash__ is not automatically suppressed in that version. -- ~Ethan~ -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14617 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14617] confusing docs with regard to __hash__
Changes by Éric Araujo mer...@netwok.org: -- versions: -Python 2.7 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14617 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14617] confusing docs with regard to __hash__
Ethan Furman et...@stoneleaf.us added the comment: More re-writing... -- Added file: http://bugs.python.org/file25264/__hash__2.diff ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14617 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
