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POcallable as instancemethod?
 

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    <p>Let's say we've got a metaclass <code>CallableWrappingMeta</code> which walks the body of a new class, wrapping its methods with a class, <code>InstanceMethodWrapper</code>:</p> <pre><code>import types class CallableWrappingMeta(type): def __new__(mcls, name, bases, cls_dict): for k, v in cls_dict.iteritems(): if isinstance(v, types.FunctionType): cls_dict[k] = InstanceMethodWrapper(v) return type.__new__(mcls, name, bases, cls_dict) class InstanceMethodWrapper(object): def __init__(self, method): self.method = method def __call__(self, *args, **kw): print "InstanceMethodWrapper.__call__( %s, *%r, **%r )" % (self, args, kw) return self.method(*args, **kw) class Bar(object): __metaclass__ = CallableWrappingMeta def __init__(self): print 'bar!' </code></pre> <p>Our dummy wrapper just prints the arguments as they come in. But you'll notice something conspicuous: the method isn't passed the instance-object receiver, because even though <code>InstanceMethodWrapper</code> is callable, it is not treated as a function for the purpose of being converted to an instance method during class creation (after our metaclass is done with it).</p> <p>A potential solution is to use a decorator instead of a class to wrap the methods -- that function will become an instance method. But in the real world, <code>InstanceMethodWrapper</code> is much more complex: it provides an API and publishes method-call events. A class is more convenient (and more performant, not that this matters much).</p> <p>I also tried some dead-ends. Subclassing <code>types.MethodType</code> and <code>types.UnboundMethodType</code> didn't go anywhere. A little introspection, and it appears they decend from <code>type</code>. So I tried using both as a metaclass, but no luck there either. It might be the case that they have special demands as a metaclass, but it seems we're in undocumented territory at this point.</p> <p>Any ideas?</p>
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    1. USDavid Schoonover
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    1. COCan you please explain more? I am having trouble understanding what you are trying to do.
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