* Alan G Isaac <alan.is...@gmail.com> [2009-07-19 13:48:16 +0000]: > Are user defined classes hashable? > (The classes; *not* the instances!) > > I want to use some classes as dictionary keys. > Python is not objecting, > but I'm not sure how to think about > whether this could be dangerous. > I'm inclined to guess it will be hashed by id > and this is OK.
You can check for yourself: In [1]: class Foo(object): ...: pass ...: In [2]: foo = Foo() In [3]: hash hash In [3]: hash(foo) Out[3]: 15294992 In [4]: id(foo) Out[4]: 15294992 So yes, by default, user-defined classes are hashable, by id. You can override this behaviour by defining the __hash__ special method on your object. HTH, -- Nicolas Dandrimont
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