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copied!<p>The problem is that by writing <code>super(MyClass, self).__init__(text)</code>, you are saying to use the super relative to whatever class <code>MyClass</code> refers to at the time <code>super</code> is called. But the decorator replaces <code>MyClass</code> with a subclass of itself. So when your original <code>__init__</code> method is called <code>MyClass</code> actually refers to a subclass of the class which defines the executing method.</p> <p>To say it step by step, I'm going to call the original class (as written in the source) <code>OrigMyClass</code>, and the resulting version (after the decorator) <code>DecMyClass</code>. I'll use <code>MyClass</code> just as a variable, because its meaning changes during the course of execution.</p> <ol> <li><p>You define an <code>__init__</code> method on <code>OrigMyClass</code>, but that <code>__init__</code> method calls <code>super(MyClass, self)</code>, not <code>super(OrigMyClass, self)</code>. Thus, what method will actually be called depends on what <code>MyClass</code> refers to <em>at the time the method is called</em>. The value of <code>MyClass</code> is looked up at execution time like any other variable; placing it inside the <code>super</code> call or inside the <code>__init__</code> method does not magically bind it to the class it happens to be in when you write it; variables in functions are evaluated when they are called, not when they are defined.</p></li> <li><p>The decorator runs. The decorator defines a new class <code>DecMyClass</code> as a subclass of <code>OrigMyClass</code>. <code>DecMyClass</code> defines an <code>__init__</code> that calls <code>super(DecMyClass, self)</code>.</p></li> <li><p>After the decorator runs, the name <code>MyClass</code> is bound to the class <code>DecMyClass</code>. Note that this means that when the <code>super(MyClass, self)</code> call later executes, it will be doing <code>super(DecMyClass, self)</code>.</p></li> <li><p>When you do <code>MyClass(111)</code>, you instantiate an object of <code>DecMyClass</code>. <code>DecMyClass.__init__</code> calls <code>super(DecMyClass, self).__init__</code>. This executes <code>OrigMyClass.__init__</code>.</p></li> <li><p><code>OrigMyClass.__init__</code> calls <code>super(MyClass, self).__init__</code>. Because <code>MyClass</code> refers to <code>DecMyClass</code>, this is the same as <code>super(DecMyClass, self).__init__</code>. But <code>DecMyClass</code> is a subclass of <code>OrigMyClass</code>. The key point is that because <code>MyClass</code> refers to <code>DecMyClass</code>, <code>OrigMyClass</code> is actually calling super <em>on a subclass of itself</em>.</p></li> <li><p>Thus <code>super(DecMyClass, self).__init__</code> again calls <code>OrigMyClass.__init__</code>, which again calls itself, and so on to infinity.</p></li> </ol> <p>The effect is the same as this code, which may make the execution path more obvious:</p> <pre><code>>>> class Super(object): ... def __init__(self): ... print "In super init" ... super(Sub, self).__init__() >>> class Sub(Super): ... def __init__(self): ... print "In sub init" ... super(Sub, self).__init__() </code></pre> <p>Note that <code>Super</code> calls <code>super(Sub, self)</code>. It is trying to call a superclass method, but it tries to call the superclass method of <code>Sub</code>. The superclass of <code>Sub</code> is <code>Super</code>, so <code>Super</code> winds up calling its own method again.</p> <p>Edit: Just to clarify the name-lookup issues you raised, here's another slightly different example that has the same result:</p> <pre><code>>>> class Super(object): ... def __init__(self): ... print "In super init" ... super(someClass, self).__init__() >>> class Sub(Super): ... def __init__(self): ... print "In sub init" ... super(Sub, self).__init__() >>> someClass = Sub </code></pre> <p>This should make it clear that the class argument to <code>super</code> (the first argument, here <code>someClass</code>) is not special in any way. It is just an ordinary name whose value is looked up in the ordinary way at the ordinary time, namely when the <code>super</code> call is executed. As shown by this example, the variable doesn't even have to exist at the time you define the method; the value is looked up at the time you <em>call</em> the method.</p>

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