[issue14671] isinstance(obj, object) returns True for _old style_ class instances
Q abon...@gmail.com added the comment: thanks, that's rather convenient -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14671 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14671] isinstance(obj, object) returns True for _old style_ class instances
Changes by Ezio Melotti ezio.melo...@gmail.com: -- nosy: +ezio.melotti ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14671 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14671] isinstance(obj, object) returns True for _old style_ class instances
Georg Brandl ge...@python.org added the comment: This is a result of how old-style classes are implemented. If you look at type(Old()), you can see that it isn't Old, but instance. (And instance is a subclass of object again.) issubclass for old-style classes doesn't check type(o) but o.__class__, which are different: the former is instance and the latter your class. That is one reason we removed old-style classes in Python 3... -- nosy: +georg.brandl resolution: - wont fix status: open - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14671 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14671] isinstance(obj, object) returns True for _old style_ class instances
Q abon...@gmail.com added the comment: I do not mean to reopen the bug (there are supposedly much more important things to work on in Python). But just for the record, let me state that I feel like there is some misleading inconsistency here: - by definition, a new style class is Any class which inherits from object ( see http://docs.python.org/glossary.html#term-new-style-class ) ; - to support this statement, new classes are indeed explicitly defined in the form NewClass(object) ; - now isinstance(), that is supposed to return whether an object is an instance of a class or of a subclass thereof (see help(isinstance)), returns True for old-style objects. It also seems reasonable if the descendants of a class will inherit its powers, which -- in the case of the old-style classes -- they obviously don't. Furthermore, I personally see no /point/ in returning True for isinstance(Old(), object): as it is quite misleading, one could easily have made it returning e.g. None as well. As I completely accept the fact it's a feature -- ( may be slightly confusing, and probably also useless -- but ... hey, nobody's perfect ) -- should I take then calling issubclass(obj.__class__, object) to be the official way to distinguish between the new-style and the old-style classes? -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14671 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14671] isinstance(obj, object) returns True for _old style_ class instances
Benjamin Peterson benja...@python.org added the comment: 2012/4/26 Q rep...@bugs.python.org: issubclass(obj.__class__, object) to be the official way to distinguish between the new-style and the old-style classes? Just do type(cls) is types.ClassType. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14671 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14671] isinstance(obj, object) returns True for _old style_ class instances
Changes by Q abon...@gmail.com: -- title: isinstance(obj, object) returns True for _old style_ classes - isinstance(obj, object) returns True for _old style_ class instances ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14671 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14671] isinstance(obj, object) returns True for _old style_ class instances
Q abon...@gmail.com added the comment: In addition: issubclass(Old, object) False -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14671 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14671] isinstance(obj, object) returns True for _old style_ class instances
Benjamin Peterson benja...@python.org added the comment: Yes, everything is a object. issubclass, though, works differently for old-style and new-style classes. -- nosy: +benjamin.peterson resolution: - invalid status: open - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14671 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14671] isinstance(obj, object) returns True for _old style_ class instances
Q abon...@gmail.com added the comment: help(isinstance) isinstance(...) isinstance(object, class-or-type-or-tuple) - bool Return whether an object is an instance of a class or of a subclass thereof. (...) So are the old-style class instances descendants of the object? I feel like I am missing something (except for the fact that you have closed the bug). -- resolution: invalid - status: closed - open ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14671 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
