"""Generic metaclass.
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XXX This is very much a work in progress.
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"""
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import types
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class MetaMethodWrapper:
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def __init__(self, func, inst):
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self.func = func
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self.inst = inst
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self.__name__ = self.func.__name__
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def __call__(self, *args, **kw):
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return apply(self.func, (self.inst,) + args, kw)
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class MetaHelper:
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__methodwrapper__ = MetaMethodWrapper # For derived helpers to override
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def __helperinit__(self, formalclass):
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self.__formalclass__ = formalclass
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def __getattr__(self, name):
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# Invoked for any attr not in the instance's __dict__
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try:
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raw = self.__formalclass__.__getattr__(name)
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except AttributeError:
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try:
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ga = self.__formalclass__.__getattr__('__usergetattr__')
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except (KeyError, AttributeError):
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raise AttributeError, name
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return ga(self, name)
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if type(raw) != types.FunctionType:
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return raw
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return self.__methodwrapper__(raw, self)
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class MetaClass:
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"""A generic metaclass.
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This can be subclassed to implement various kinds of meta-behavior.
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"""
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__helper__ = MetaHelper # For derived metaclasses to override
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__inited = 0
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def __init__(self, name, bases, dict):
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try:
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ga = dict['__getattr__']
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except KeyError:
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pass
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else:
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dict['__usergetattr__'] = ga
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del dict['__getattr__']
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self.__name__ = name
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self.__bases__ = bases
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self.__realdict__ = dict
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self.__inited = 1
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def __getattr__(self, name):
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try:
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return self.__realdict__[name]
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except KeyError:
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for base in self.__bases__:
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try:
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return base.__getattr__(name)
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except AttributeError:
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pass
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raise AttributeError, name
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def __setattr__(self, name, value):
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if not self.__inited:
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self.__dict__[name] = value
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else:
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self.__realdict__[name] = value
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def __call__(self, *args, **kw):
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inst = self.__helper__()
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inst.__helperinit__(self)
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try:
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init = inst.__getattr__('__init__')
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except AttributeError:
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init = lambda: None
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apply(init, args, kw)
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return inst
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Meta = MetaClass('Meta', (), {})
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def _test():
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class C(Meta):
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def __init__(self, *args):
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print "__init__, args =", args
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def m1(self, x):
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print "m1(x=%r)" % (x,)
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print C
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x = C()
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print x
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x.m1(12)
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class D(C):
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def __getattr__(self, name):
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if name[:2] == '__': raise AttributeError, name
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return "getattr:%s" % name
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x = D()
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print x.foo
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print x._foo
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## print x.__foo
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## print x.__foo__
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if __name__ == '__main__':
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_test()
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