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  1. from types import prepare_class
  2.  
  3. def combine_meta(name, bases, namespace, **kwargs):
  4.     metaclasses = []
  5.     for base in bases:
  6.         meta, ns, _ = prepare_class(name, (base,), kwargs)
  7.         if meta is not type:
  8.             if type(ns) is not type(namespace):
  9.                 if type(namespace) is not dict:
  10.                     raise TypeError('metaclass conflict: '
  11.                         'multiple custom namespaces defined.')
  12.                 ns.update(namespace)
  13.                 namespace = ns
  14.             elif ns:
  15.                 namespace.update(ns)
  16.             metaclasses = [other for other in metaclasses if not issubclass(meta, other)]
  17.             if not any(issubclass(other, meta) for other in metaclasses):
  18.                 metaclasses.append(meta)
  19.     if len(metaclasses) > 1:
  20.         meta_name = '_'.join(meta.__name__ for meta in metaclasses)
  21.         print(metaclasses)
  22.         metaclass = type(meta_name, tuple(metaclasses), {})
  23.     else:
  24.         metaclass, = metaclasses or (type,)
  25.     return metaclass(name, bases, namespace, **kwargs)
  26.  
  27. class M1(type):
  28.     pass
  29.  
  30. class M2(M1):
  31.     pass
  32.  
  33. class A(metaclass=M1):
  34.     pass
  35.  
  36. class B(metaclass=M2):
  37.     pass
  38.  
  39. class C(A, B, metaclass=combine_meta):
  40.     pass
  41.  
  42. assert type(C) is M2
  43.  
  44. class C(B, A, metaclass=combine_meta):
  45.     pass
  46.  
  47. assert type(C) is M2
Success #stdin #stdout 0.03s 9600KB
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https://ideone.com/kpd4pi
language:
Python 3 (python  3.9.5)
created:
71 days ago
visibility:
secret

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