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Author	gvanrossum
Date	2007年04月26日.20:16:58
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Content
I came up with a fairly simple way to overload isinstance() and issubclass(). The class that is the second argument can define a (class) method named __instancecheck__ or __subclasscheck__ which, if present, will be called instead of the normal approach. The names are different to remind users that the calling convention is the opposite -- isinstance(x, C) maps to C.__instancecheck__(x).

Content

I came up with a fairly simple way to overload isinstance() and issubclass(). The class that is the second argument can define a (class) method named __instancecheck__ or __subclasscheck__ which, if present, will be called *instead* of the normal approach.
The names are different to remind users that the calling convention is the opposite -- isinstance(x, C) maps to C.__instancecheck__(x).

History
Date	User	Action	Args
2007年08月23日 15:58:15	admin	link	issue1708353 messages
2007年08月23日 15:58:15	admin	create