Property Abuse

[Ian Kelly]

On Wed, Dec 14, 2011 at 1:28 AM, Felipe O <pip.261 at gmail.com> wrote:
> Hi All,
> I was wondering what everyone's thought process was regarding properties.
> Lately I find I've been binging on them and have classes with > 10
> properties. While pylint doesn't complain (yet), it tends to be picky about
> keeping instance attribute counts low, so I figure there's something against
> that. How do you guys decide between using properties versus getter methods,
> or how do you refactor them if neither?

I prefer direct instance attribute access where possible*, properties
where necessary, and methods where an argument is needed or the
relationship is more complex than get/set/delete.

* One of the strengths of Python's property system** is that you can
switch between plain attributes and mutable properties as needed
without breaking dependent code.  Often I see people doing this, which
drives me nuts with its useless verbosity, when a plain instance
attribute would have sufficed:

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

    @foo.setter
    def foo(self, value):
        self._foo = value

** As opposed, for instance, to the .NET property system.  You can't
arbitrarily switch between public member variables and public
properties in .NET, because it breaks ABI.

Cheers,
Ian