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.

Looks great (regardless of how this is implemented).  I always hated this
def get_foo / def set_foo / foo = property (get_foo, set_foo).

propset2.diff is a new version that improves upon the heuristic for
making the deleter match the setter: when changing setters, if the old
deleter is the same as the old setter, it will replace both the deleter
and setter.

This diff is relative to the 2.6 trunk; it applies to 3.0 too.

propset3.diff removes the hack that makes the deleter equal to the
setter when no separate deleter has been specified.  If you want a
single method to be used as setter and deleter, write this:

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

Fixed a typo:

+PyDoc_STRVAR(getter_doc,
+            "Descriptor to change the setter on a property.");
                                      ^^^

Checked into trunk as revision 58929.