[Python-Dev] DRAFT: pydev summary for 2006-12-01 to 2006-12-15 (original) (raw)
Walter Dörwald walter at livinglogic.de
Tue Jan 9 14:02:10 CET 2007
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Calvin Spealman wrote:
[...] ----------------------------------- Creating dicts from dict subclasses -----------------------------------
A common problem of subclassing built-in types (dict, in this case) arose trying to move weakref.WeakValueDictionary to a subclass of dict, rather than UserDict. [NOTE: Could someone give a better description of this? I don't know enough of the issue here to write any content full enough. Thanks.]
The problem is that if you pass a mapping (i.e. something with a keys() method) to the dict constructor, it uses keys() and getitem() to make a copy. However if the argument is a subclass of dict, any overwritten keys() or getitem() methods are ignored.
Servus, Walter
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