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POUsing super() in a property's setter method when using the @property decorator raises an AttributeError
 

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  1. POUsing super() in a property's setter method when using the @property decorator raises an AttributeError
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    <p>I am a little confused by the behavior when attempting to overwrite a property in a subclass. </p> <p>The first example sets up two classes, <code>Parent</code> and <code>Child</code>. <code>Parent</code> inherits from <code>object</code>, while <code>Child</code> inherits from <code>Parent</code>. The property <code>a</code> is defined using the property decorator. When <code>child.a</code>'s setter method is called, an <code>AttributeError</code> is raised. </p> <p>In the second example, by using the <code>property()</code> function rather than the decorator, everything works as would be expected.</p> <p>Can anyone shed some light on why the behavior differs? Also, yes, I know that the <code>__init__</code> definition in Child is not needed.</p> <h3>Example 1 - Using <code>@property</code></h3> <pre><code>class Parent(object): def __init__(self): self._a = 'a' @property def a(self): return self._a @a.setter def a(self, val): self._a = val class Child(Parent): def __init__(self): super(Child, self).__init__() @property def a(self): return super(Child, self).a @a.setter def a(self, val): val += 'Child' super(Child, self).a = val p = Parent() c = Child() print p.a, c.a p.a = 'b' c.a = 'b' print p.a, c.a </code></pre> <h3>Example 1 return - Raises an attribute error</h3> <pre><code>a a Traceback (most recent call last): File "testsuper.py", line 26, in &lt;module&gt; c.a = 'b' File "testsuper.py", line 20, in a super(Child, self).a = val AttributeError: 'super' object has no attribute 'a' </code></pre> <h3>Example 2 - <code>Using property()</code></h3> <pre><code>class Parent(object): def __init__(self): self._a = 'a' def _get_a(self): return self._a def _set_a(self, val): self._a = val a = property(_get_a, _set_a) class Child(Parent): def __init__(self): super(Child, self).__init__() def _get_a(self): return super(Child, self)._get_a() def _set_a(self, val): val = val+'Child' super(Child, self)._set_a(val) a = property(_get_a, _set_a) p = Parent() c = Child() print p.a, c.a p.a = 'b' c.a = 'b' print p.a, c.a </code></pre> <h3>Example 2 return - Works correctly</h3> <pre><code>a a b bChild </code></pre>
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    1. COMy first advice is not to use the decorator form in this case. (I find it actually annoying but for read only properties)
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    2. COEven so, kind of an odd issue.
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    3. COI get a different error for Example 1 on line 12 `super(Child, self).a = val` -- `TypeError: super(type, obj): obj must be an instance or subtype of type`.
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