python abstract property setter with concrete getter

Question

is it possible to use abc.abstractproperty to create a concrete getter but make the setter abstract so its different for each of the inheriting classes. I handle the setting of val different for each subclass.

eg.

@abstractproperty
def val(self):
    return self._val

@val.setter
def val(self, x):
    pass

Answer 1

You'll need a little bit of indirection. Define the setter as you normally would, but have it call an abstract method that does the actual work. Then each child class will need to provide a definition of that method. For example,

class Base(object):
    __metaclass__ = abc.ABCMeta

    def __init__(self):
        self._val = 3

    @property
    def val(self):
        return self._val

    @val.setter
    def val(self, x):
        self._val_setter(x)

    @abc.abstractmethod
    def _val_setter(self, x):
        pass


class Child(Base):

    def _val_setter(self, x):
        self._val = 2*x

Then

>>> c = Child()
>>> print c.val
3
>>> c.val = 9
>>> print c.val
18