Marc Aymerich wrote:
> On Feb 2, 12:11 am, Peter Otten <__pete...@web.de> wrote:
>> Marc Aymerich wrote:
>> > Hi all,
>> > I want to provide an encapsulated static attribute called _registry
>> > for several classes.
>>
>> > I try to use inheritance in order to make it DRY: all classes inherit
>> > from a BaseClass that implements the _registry encapsulation. But with
>> > inheritance it doesn't work how I want, because a single instance of
>> > the _registry is shared between all of the inherited classes, and I
>> > want to have an independent _registry for every class.
>>
>> > How can I do that without coping all the code in every class?
>>
>> If you want to go fancy use a metaclass:
>>
>> >>> class Base(object):
>>
>> ... class __metaclass__(type):
>> ... def __init__(self, *args):
>> ... type.__init__(self, *args)
>> ... self.per_class = []
>
>
> Many thanks Peter!!
Here's a variant that doesn't rely on the metaclass:
class Base(object):
registries = {}
@property
def per_class(self):
cls = type(self)
try:
return self.registries[cls]
except KeyError:
result = self.registries[cls] = []
return result
class A(Base): pass
class B(Base): pass
assert A().per_class is A().per_class
assert B().per_class is B().per_class
assert A().per_class is not B().per_class
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