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POOverwriting a field's method in Python
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copied!<p>I have a custom class which I instantiate twice in a second class:</p> <p>[EDIT: The old code wasn't really capturing what my issue is, I'm rewriting to make it clearer. Foo is going to process network events (and I need multiple connections, hence why Bar will have multiple Foo fields and can't just inherit) by using a callback function. In the Bar class, i want to overwrite the callback to do something different. Rewriting callb in Foo won't work, because I do inherit from it in other instances]</p> <pre><code>class Foo(object): def __init__(self, x): self._x = x #When an event happens, call callb() self.on_certain_event(callback=callb) def callb(self): print self._x def run(self): waitForEventsInfinitely() # class Bar(object): def __init__(self): self._foo = Foo(5) #OVERWRITE THE EXISTING CALLBACK METHOD IN THE Foo CLASS! self._foo.callb = self.callb def callb(self): print self._x * 10 def run(self): waitForEventsInfinitely() # Not going to actually write t f = Foo(2) f.run() b = Bar() b.run() </code></pre> <p>[When run() is called in a Foo, it works correctly. However, I cannot overwrite the callb method of Foo from Bar - the self._x which should be referred to by Foo is trying to call from Bar]</p> <p>However, when running the code, I receive the error "Bar has no attribute '_x'" rather than my expected value of 50. Obviously, the self in Bar's test is still referring to Bar, not the Foo which is actually calling the method. I would have expected it to be the internal Foo self._foo field in Bar.</p> <p>I suspect my problem has something to do with name mangling, but I haven't been able to find a descriptive source when I have fields on self having their methods overwritten. Most examples seem to be when I'm inheriting from a different class.</p>

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