Le Thursday 04 September 2008 23:35:18 Terry Reedy, vous avez écrit : > Maric Michaud wrote: > > Le Thursday 04 September 2008 22:26:53 Ruediger, vous avez écrit : > >> class foo(list): > >> __hash__ = lambda x: id(x) > > > > Wow ! You are really going on trouble with this, believe me there is a > > real good reason for list not to be hashable. A dictionnary or set > > containing some of your foo is virtually inconsistent, read carefully the > > manual about prerequesites for dict keys, they *need* to be immutable. > > No, the id comparison needs to be immutable -- which it is by default > for object()s, being based on id. Mutable instances of classes derived > from object work fine as keys as long as they keep default __eq__ and > __hash__. List over-rides the default, so foo needs to reverse that > override: > def __eq__(self, other): > return id(self) == id(other) > > This means, of course, that foo loses value-based equality comparison.
Yes, so what's the point of using lists as keys. "class a : pass" already do this. -- _____________ Maric Michaud -- http://mail.python.org/mailman/listinfo/python-list
