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POpython - trying to override __getattr__ for dynamically added class but only sort of works
 

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    <p>I am trying to add a new class to an existing class at run time (using "type(...)"). I am also trying to override that new class' __getattr__ so that I can do my own behavior on attributes that are not in the new class. For example, I have class foo, I add class "tool" and I want foo.tool.test to do something of my own. The code below works but only partly. If I explicitly call __getattr__, it works (see first print) but when I reference foo.tool.test, my overridden __getattr__ does not get called and an attrbute error is raised. </p> <p>Your help is greatly appreciated.</p> <pre><code>class Foo(object): def __init__(self): self.NameList=[] # add new class to ourself self.tool = type('tool', (object,), {} ) # override new class' __getattr__ with call to ourself setattr(self.tool, "__getattr__", self.__getattr__ ) # add one well known test name for now self.NameList.append( "test" ) # should be called by our newly added "tool" object but is only called sometimes... def __getattr__(self, attr): # print( "__getattr__: %s" % attr ) if( attr in self.NameList ): return( 99 ) raise AttributeError("--%r object has no attribute %r" % (type(self).__name__, attr)) foo = Foo() # access tool class attribute "test" - it should be seen by the override __getattr__ # the following works... print( "foo.tool.__getattr__=%d" % foo.tool.__getattr__("test") ) # but the following does not - why is this not the same as the line above??? print( "foo.tool.test=%d" % foo.tool.test ) </code></pre>
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    1. COYou refer to `tool` as a class, but also as the `object`. The `__getattr__` will work ok on an instance of `tool`. eg `foo.tool().test`
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      1. POpython - trying to override __getattr__ for dynamically added class but only sort of works
      1. USJohn La Rooy
 

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