override-decorators.py

class Top:
  @property
  def foo(self):
    ...
  @foo.setter
  def set_foo(self, value):
    ...

class Spam(Top):
  @property
  def foo(self)
    return super().foo
  
  @foo.setter
  def foo(self, value):
    super().foo = value
    ...

override-props.py

class Top:
  def get_foo(self):
    ...
  def set_foo(self, value):
    ...
  foo = property(get_foo, set_foo)

class Spam(Top):
  # Probably the simplest, but ignores MRO
  def set_foo(self, value):
    super().set_foo(value)
    ...
  foo = property(Top.get_foo, set_foo)
  
class Eggs(Top):
  # More complicated, but respects MRO
  def set_foo(self, value):
    super().set_foo(value)
    ...
  foo = property(
    (lambda self: self.get_foo()),
    (lambda self, value: self.set_foo(value)
  )

class Sausage(Top):
    # This just won't work
  def set_foo(self, value):
    super().set_foo(value)
    ...

In override-decorators.py, this code doesn't make sense:

  @foo.setter
  def set_foo(self, value):
    ...

The setter definition should be named foo, too, or the setting property won't be available as foo. (In other words, foo will remain a read-only property, while set_foo will become a new property that both gets (with foo's getter) and sets.)

Here's a working example of property extension:

class Top:

    @property
    def foo(self):
        …

    @foo.setter
    def foo(self, value):
        …


class Spam(Top):

    @property
    def foo(self):
        return super().foo

    @foo.setter
    def foo(self, value):
        # This is the tricky bit: super() seems to only implement getting, not setting. (?)
        # So, we have to simulate super().foo = value
        super(Spam, type(self)).foo.fset(self, value)