attributes, properties, and accessors -- philosophy

[Chris Rebert]

On Tue, Nov 24, 2009 at 9:39 AM, Ethan Furman <ethan at stoneleaf.us> wrote:
> Bruno Desthuilliers wrote:
>> Ethan Furman a écrit :
>>> The problem I have with properties is my typing.  I'll end up assigning
>>> to an attribute, but get the spelling slightly wrong (capitalized, or
>>> missing an underscore -- non-obvious things when bug-hunting), so now I have
>>> an extra attribute which of course has zero effect on what I'm trying to do
>>> and I start getting wierd results like viewing deleted records when I *know*
>>> I set useDeleted = False... 30 minutes later I notice it was /supposed/ to
>>> be use_deleted.  *sigh*
>>>
>>> So -- to keep myself out of trouble -- I have started coding such things
>>> as, for example:
>>>
>>> result = table.use_deleted()       # returns True or False
>>> table.use_deleted(False)           # skip deleted records
>>>
>>> instead of
>>>
>>> result = table.use_deleted
>>> table.use_deleted = False
>>>
>>> My question:  is this [ severely | mildly | not at all ] un-pythonic?
>>
>>
>> Definitly and totally unpythonic. The first solution to your problem is to
>> stick to standard naming conventions. If this is not enough, Chris pointed
>> you to really useful tools. Also, you can override __setattr__ to catch such
>> errors - at least during the coding/debug phase.
>
> Good tools to know about, and a consistent naming pattern also makes life
> easier (which I have since done ;).
>
> Let's head towards murkier waters (at least murkier to me -- hopefully they
> can be easily clarified):  some of the attributes are read-only, such as
> record count; others are not directly exposed, but still settable, such as
> table version; and still others require a small amount of processing... at
> which point do I switch from simple attribute access to method access?

Thanks to the magic of properties, the end-user-programmer need not
know which you're using:

http://docs.python.org/library/functions.html#property

Cheers,
Chris
--
http://blog.rebertia.com