On Thu, Jun 23, 2016 at 8:19 AM, Guido van Rossum <gu...@python.org> wrote: > > It was a long time when I wrote this, but IIRC the breakage could express > itself as a segfault or other C-level crash due to some internal state > invariant of the type object being violated, not just an exception. The > existence of ctypes notwithstanding, we take C-level crashes very seriously. >
Big digression: one can still obtain the dict if they really want to, even without using ctypes. I suppose don't actually mutate it unless you want to segfault. >>> import gc >>> class A(object): pass >>> type(A.__dict__) <class 'mappingproxy'> >>> type(gc.get_referents(A.__dict__)[0]) <class 'dict'> >>> gc.get_referents(A.__dict__)[0]['abc'] = 1 >>> A.abc 1 >>> (One can also get it right from A, but A can have other references, so maybe that's less reliable.) I think I wanted this at the time so I could better measure the sizes of objects. sys.getsizeof(A.__dict__) is very different from sys.getsizeof(gc.get_referents(A.__dict__)[0]), and also different from sys.getsizeof(A). For example: >>> import gc >>> class A(object): pass >>> sys.getsizeof(A); sys.getsizeof(A.__dict__); sys.getsizeof(gc.get_referents(A.__dict__)[0]) 976 48 288 >>> for i in range(10000): setattr(A, 'attr_%s' % i, i) >>> sys.getsizeof(A); sys.getsizeof(A.__dict__); sys.getsizeof(gc.get_referents(A.__dict__)[0]) 976 48 393312 (Fortunately, if you want to walk the object graph to measure memory usage per object type, you're probably going to be using gc.get_referents already anyway, so this is just confirmation that you're getting what you want in one corner case.) -- Devin
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