[Tutor] Accessing class attributes: use methods only?

[Dave Kuhlman]

On Tue, Feb 13, 2007 at 11:35:47PM -0500, Kent Johnson wrote:
> Bob Gailer wrote:
> > I really like the simplicity of a.b = 3. I groan when put in other 
> > environments where a method call is required.
> > 
> > And Python has the magic method __setattr__ to intercept attribute 
> > assignment for the times where some inspection / protection / 
> > side-effect action is desired.
> 
> The modern way to do this (since Python 2.2 I think) is to use 
> properties. __setattr__ has other uses (for example for delegation) but 
> it is too big a hammer for changing the behaviour of a single attribute.

NTSAAB (Not to start an argument but) ...

Some of us old school types feel that properties are non-Pythonic. 
They are a way to write code that does something that it does not
look like that code is doing.  It hides your intend.  So, it is not
explicit.

    "Explicit is better than implicit."
                   - Tim Peters
                     (see http://www.python.org/dev/peps/pep-0020/)

In other words, properties are a way of writing code that appears
harmless, for example:

    temp = weather.temperature

and:

    weather.temperature = temp

but making it do arbitrary, sneaky, gratuitous, and egregious things.
See the documentation on the *property* function at
http://www.python.org/dev/peps/pep-0020/.

However, some of you are probably saying to yourselves: "Well, of
course (we're sneaky; we're devious; ...).  I mean we are
programmers, after all."

OK. OK. Maybe I had too much coffee this morning.

Dave

-- 
Dave Kuhlman
http://www.rexx.com/~dkuhlman