[Python-Dev] Creating dicts from dict subclasses (original) (raw)
Walter Dörwald walter at livinglogic.de
Wed Dec 13 17:57:16 CET 2006
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I tried to reimplement weakref.WeakValueDictionary as a subclass of dict. The test passes except for one problem: To compare results test_weakref.py converts a weakdict to a real dict via dict(weakdict). This no longer works because PyDict_Merge() does a PyDict_Check() on the argument and then ignores all overwritten methods. (The old version worked because UserDict.UserDict was used).
The simplest solution is to replace the PyDict_Check() call with PyDict_CheckExact(), but this might slow things down too much, because the fallback code basically does:
for key in iter(arg.keys()): self[key] = arg.getitem(key)
Why can't we use:
for key in iter(arg): self[key] = arg.getitem(key)
instead?
Servus, Walter
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