Matthew Wilson wrote:
> I sometimes inadvertently create a new attribute on an object rather
> update a value bound to an existing attribute. For example:
>
(snip)
>
> I meant to update c.a but I created a new c.A. I make this mistake
> probably hourly.
>
> I suspect adding attributes at run time can be a beautiful thing, but in
> this particular instance, I'm only using this feature to hurt myself.
See other posts in this thread for some other possible solutions.
> I wrote a simple class that will warn me when I make this mistake in the
> future:
>
> import warnings
>
> class C(object):
>
> warn_on_new_attributes = True
>
> standard_attributes = []
>
> def __setattr__(self, name, value):
>
> if self.warn_on_new_attributes \
> and name is not 'warn_on_new_attributes' \
> and name not in self.standard_attributes:
>
> warnings.warn("%s has no standard attribute %s."
> % (self.__class__.__name__, name))
>
>
> self.__dict__[name] = value
Make it:
object.__setattr__(self, name, value)
Your approach will lead to strange results if you mix it with properties
or other descriptors...
> class C1(C):
>
> standard_attributes = ['a1', 'a2']
DRY violation here. And a potential problem with inheritance (as always
with class attributes).
(snip)
--
bruno desthuilliers
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