At 01:39 PM 10/24/03 -0700, Zack Weinberg wrote:
>class foo:
> A = 1 # these are class variables
> B = 2
> C = 3
>
> def __init__(self):
> self.a = 4 # these are instance variables
> self.b = 5
> self.c = 6
>
>I find this imperative syntax for declaring instance variables
>profoundly unintuitive. Further, on my first exposure to Python, I
>thought A, B, C were instance variables, although it wasn't hard to
>understand why they aren't.
A, B, and C *are* instance variables. Why do you think they aren't?
>People like to rag on the popularity of __slots__ (for reasons which
>are never clearly spelled out, but never mind) -- has anyone
>considered that it's popular because it's a way of declaring the set
>of instance variables,
What good does declaring the set of instance variables *do*? This seems to
be more of a mental comfort thing than anything else. I've spent most of
my career in declaration-free languages, though, so I really don't
understand why people get so emotional about being able to declare their
variables.
> and there is no other way in the language?
Actually, there are a great many ways to implement such a thing. One way
might be something like:
class RestrictedVars:
vars = ()
def __setattr__(self,attr,name):
if name not in self.vars:
raise AttributeError("No such attribute",attr)
class SomeClass(RestrictedVars):
vars = 'a','b','c'
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