[Python-Dev] Declaring setters with getters (original) (raw)

Fred Drake fdrake at acm.org
Thu Nov 1 02:38:27 CET 2007

On Oct 31, 2007, at 4:28 PM, Guido van Rossum wrote:

Given how rarely supporting deletions matters enough to write extra code, we can just say that when using @propset your setter function needs to have a default value for the argument or otherwise support being called with one or two arguments.

It's definitely unusual, but the logic is typically very different;
conflating the method in Python doesn't really feel "right" to me.

I've been using Philipp von Weitershausen's "rwproperty" quite happily:

http://pypi.python.org/pypi/rwproperty/

It uses the names "getproperty", "setproperty", and "delproperty",
which feel reasonable when I use them (always referenced using the
module), like so:

class Thing(object):

   @rwproperty.setproperty
   def attribute(self, value):
       # ...

If I had to choose built-in names, though, I'd prefer "property",
"propset", "propdel". Another possibility that seems reasonable
(perhaps a bit better) would be:

class Thing(object):

   @property
   def attribute(self):
       return 42

   @property.set
   def attribute(self, value):
       self._ignored = value

   @property.delete
   def attribute(self):
       pass

-Fred

-- Fred Drake

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