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  1. PO
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    <p>Here's how I would do this:</p> <pre><code>class ClassPropertyDescriptor(object): def __init__(self, fget, fset=None): self.fget = fget self.fset = fset def __get__(self, obj, klass=None): if klass is None: klass = type(obj) return self.fget.__get__(obj, klass)() def __set__(self, obj, value): if not self.fset: raise AttributeError("can't set attribute") type_ = type(obj) return self.fset.__get__(obj, type_)(value) def setter(self, func): if not isinstance(func, (classmethod, staticmethod)): func = classmethod(func) self.fset = func return self def classproperty(func): if not isinstance(func, (classmethod, staticmethod)): func = classmethod(func) return ClassPropertyDescriptor(func) class Bar(object): _bar = 1 @classproperty def bar(cls): return cls._bar @bar.setter def bar(cls, value): cls._bar = value # test instance instantiation foo = Bar() assert foo.bar == 1 baz = Bar() assert baz.bar == 1 # test static variable baz.bar = 5 assert foo.bar == 5 # test setting variable on the class Bar.bar = 50 assert baz.bar == 50 assert foo.bar == 50 </code></pre> <p>The setter didn't work at the time we call <code>Bar.bar</code>, because we are calling <code>TypeOfBar.bar.__set__</code>, which is not <code>Bar.bar.__set__</code>.</p> <p>Adding a metaclass definition solves this:</p> <pre><code>class ClassPropertyMetaClass(type): def __setattr__(self, key, value): if key in self.__dict__: obj = self.__dict__.get(key) if obj and type(obj) is ClassPropertyDescriptor: return obj.__set__(self, value) return super(ClassPropertyMetaClass, self).__setattr__(key, value) # and update class define: # class Bar(object): # __metaclass__ = ClassPropertyMetaClass # _bar = 1 # and update ClassPropertyDescriptor.__set__ # def __set__(self, obj, value): # if not self.fset: # raise AttributeError("can't set attribute") # if inspect.isclass(obj): # type_ = obj # obj = None # else: # type_ = type(obj) # return self.fset.__get__(obj, type_)(value) </code></pre> <p>Now all will be fine.</p>
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    1. POHow to make a class property?
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    1. USmartineau
    1. USMahmoud Abdelkader
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    1. POHow to make a class property?
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    1. VO
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      1. VTUpMod
    2. VO
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    1. COhmm.. my setter function appears to be ignored, and I can't get anything in __set__ to execute ever (even if i just some garbage in there, nothing changes)
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      1. USKyle Wild
    2. COthe 2nd assertion here fails: http://drktd.com/6D2b
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      1. USKyle Wild
    3. COSeems to not works with setter.
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      1. USI159
 

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