Here's an implementation of the idea I floated recently on python-dev
(Subject: Declaring setters with getters).  This implements the kind of
syntax that I believe won over most folks in the end:

  @property
  def foo(self): ...

  @foo.setter
  def foo(self, value=None): ...

There are also .getter and .deleter descriptors.  This includes the hack
that if you specify a setter but no deleter, the setter is called
without a value argument when attempting to delete something.  If the
setter isn't ready for this, a TypeError will be raised, pretty much
just as if no deleter was provided (just with a somewhat worse error
message :-).

I intend to check this into 2.6 and 3.0 unless there is a huge cry of
dismay.  Docs will be left to volunteers as always.