Arnaud Delobelle wrote:
> On Apr 12, 8:36 pm, Charles D Hixson <[EMAIL PROTECTED]>
> wrote:
>
>> I'm trying to construct read-only variables at the class level. I've
>> been unsuccessful. Any suggestions?
>>
>> Mixing @classmethod and @property doesn't appear to produce workable
>> code. Ditto for mixing @classmethod and __getattr__. (The property
>> approach compiles, but execution says that you can't execute properties.)
>>
>> I've got a rather large number of variables, so I don't want to define
>> function accessors for each of them, and I *REALLY* don't want to have
>> to access them as functions rather than variables or properties.
>>
>
> Metaclasses, of course!
>
>
>>>> class MetaX(type):
>>>>
> ... @property
> ... def spam(self): return 'eggs'
> ...
>
>>>> class X(object):
>>>>
> ... __metaclass__ = MetaX
> ...
>
>>>> X.spam
>>>>
> 'eggs'
>
>
> HTH
>
> --
> Arnau
Thanks. I can make that work. Is it possible to move the entire
implementation of the interpretation of _valueMap, below, into
properties in some similar way? I'm referring to the part managed by
__getattr__ below.
I want a hundred or so read-only variables, and I'm not sure the best
way to achieve it.
class MetaROVars(type):
@property
def simple(self):
return "simple example working"
class test(object):
__metaclass__ = MetaROVars
_valueMap = {
"t1" : (3, "Concept decay rate", "[1, 99]"),
"t2" : (10, "TaskLink decay rate", "[1, 99]"),
}
[EMAIL PROTECTED]
def __getattr__(self, name):
if name not in test._valueMap:
raise AttributeError, name
return test._valueMap[name][0]
def describe (self, name):
if name not in test._valueMap:
raise AttributeError, name
return test._valueMap[name][1] + ", lying in the range " +
test._valueMap[name][2]
p = test()
print p.t1
print p.describe("t1")
print p.t2
print test.simple
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