55 lines
1.0 KiB
Python
55 lines
1.0 KiB
Python
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"""
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多重继承 - 一个类有两个或者两个以上的父类
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MRO - 方法解析顺序 - Method Resolution Order
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当出现菱形继承（钻石继承）的时候，子类到底继承哪个父类的方法
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Python 2.x - 深度优先搜索
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Python 3.x - C3算法 - 类似于广度优先搜索
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"""
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class A():
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def say_hello(self):
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print('Hello, A')
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class B(A):
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pass
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class C(A):
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def say_hello(self):
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print('Hello, C')
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class D(B, C):
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pass
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class SetOnceMappingMixin():
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"""自定义混入类"""
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__slots__ = ()
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def __setitem__(self, key, value):
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if key in self:
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raise KeyError(str(key) + ' already set')
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return super().__setitem__(key, value)
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class SetOnceDict(SetOnceMappingMixin, dict):
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"""自定义字典"""
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pass
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def main():
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print(D.mro())
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# print(D.__mro__)
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D().say_hello()
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print(SetOnceDict.__mro__)
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my_dict= SetOnceDict()
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my_dict['username'] = 'jackfrued'
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my_dict['username'] = 'hellokitty'
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if __name__ == '__main__':
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main()
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