mailing list wrote: > Hi all, > > I'm just looking for a quick runthrough on the differences between new > style classes and the old ones, and how to use the new ones. > > Also, how exactly do you use __slots__? I've got a 6000 object > collection, and apparently using __slots__ will save memory, but only > those attributes specified in __slots__ can be set, which suits my > project fine.
All you have to do is define a __slots__ variable in your class. Its value is a list of attribute names. Then instances of your class will only be able to have the attributes named in __slots__: >>> class foo(object): ... __slots__ = ['x', 'y'] ... >>> f=foo() >>> f.x=1 >>> f.y=2 >>> f.z=3 Traceback (most recent call last): File "<stdin>", line 1, in ? AttributeError: 'foo' object has no attribute 'z' Take a look at http://www.python.org/2.2.3/descrintro.html (search for __slots__) Note to the list: Use of __slots__ is generally discouraged, but IIUC this is exactly the use case it was designed for so I think it is OK. Kent _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
