Question re class variable
steve at pearwood.info
Tue Sep 29 14:06:13 CEST 2015
On Tue, 29 Sep 2015 09:17 pm, Anssi Saari wrote:
>> The problem is that in python you can't change a class variable through
>> an instance. The moment you try, you create an instance attribute.
> That much is clear but why does his other version of __gen_id() work
> (after a fashion)? It doesn't increment the class variable but the
> instances get an incremental id.
> The function was like this:
> def __gen_id(self):
> ty = self.__class__.__name__
> id = ''
> while id in self.__instance_registry:
> id = '%s_%d' % (ty, self.__instance_counter)
> self.__instance_counter += 1
> self.__instance_registry[id] = self
> return id
This works because it doesn't assign to self.__instance_registry itself, it
assigns to an item within the existing self.__instance_registry. So the
registry object (a dict?) gets modified in place, not re-bound or shadowed
by an instance attribute of the same name.
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