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Code: Alles auswählen

class Meta(type):
	def __new__(cls,name,bases,d):
		print 'Meta.__new__ called!'
		return super(Meta,cls).__new__(name,bases,d)
	def __init__(self,name, bases, d):
		print 'Meta.__init__ called!'
		super(Meta,self).__init__(name,bases,d)
	def __call__(self,*args):
		print 'Meta.__call__ called!'
		return super(Meta,self).__call__(*args)

class Foo:
	__metaclass__=Meta

Code: Alles auswählen

Meta.__new__ called!

Traceback (most recent call last):
  File "<pyshell#3>", line 1, in -toplevel-
    class Foo:
  File "<pyshell#0>", line 4, in __new__
    return super(Meta,cls).__new__(name,bases,d)
TypeError: Error when calling the metaclass bases
    type.__new__(X): X is not a type object (str)

Code: Alles auswählen

class Meta(type):

    def __new__(cls, name, bases, d):
        print 'Meta.__new__'
        result = type.__new__(cls, name, bases, d)
        def __init(self):
            print 'Meta.__init__'
        def __call(self):
            print 'Meta.__call__'
        setattr(result, '__init__', __init)
        setattr(result, '__call__', __call)
        return result


class BetterMeta(type):

    def __new__(cls, name, bases, d):
        print 'BetterMeta.__new__'
        result = type.__new__(cls, name, bases, d)
        def __init(self, *args, **kwargs):
            print 'BetterMeta.__init__'
            if '__init__' in d:
                d['__init__'](self, *args, **kwargs)
        def __call(self, *args, **kwargs):
            print 'BetterMeta.__call__'
            if '__call__' in d:
                d['__call__'](self, *args, **kwargs)
        setattr(result, '__init__', __init)
        setattr(result, '__call__', __call)
        return result


class Foo(object):
    __metaclass__ = Meta


class BetterFoo(object):
    __metaclass__ = BetterMeta
    def __call__(self):
        print 'BetterFoo.__call__'

if __name__ == '__main__':
    print '> erstelle foo'
    f = Foo()
    print '> rufe foo auf'
    f()
    print '> erstelle betterfoo'
    f2 = BetterFoo()
    print '> rufe betterfoo auf'
    f2()

Code: Alles auswählen

blackbird@volverine:~/Developement/area51$ python metacls.py
Meta.__new__
BetterMeta.__new__
> erstelle foo
Meta.__init__
> rufe foo auf
Meta.__call__
> erstelle betterfoo
BetterMeta.__init__
> rufe betterfoo auf
BetterMeta.__call__
BetterFoo.__call__