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  • python2与python3中__metacalss__的不同用法

    python3

    def upper_attr(future_class_name, future_class_parents, future_class_attr):
        attrs = ((name, value) for name, value in future_class_attr.items() if not name.startswith('__'))
        uppercase_attr = dict((name.upper(), value) for name, value in attrs)
        return type(future_class_name, future_class_parents, uppercase_attr)
    
    class Foo(metaclass = upper_attr):
        bar = 'bip'
    
    print(hasattr(Foo, 'bar'))
    print(hasattr(Foo, 'BAR'))
    f = Foo()
    print(hasattr(f,'bar'))
    print(hasattr(f,'BAR'))
    输出:

    False
    True
    False
    True

    Process finished with exit code 0

    python2:

    def upper_attr(futer_class_name, future_class_parent, futuer_class_attr):

       attrs = ((name, value) for name, value in futuer_class_attr.item() if name.startswith('__'))

      uppercase_attr = dict((name.upper(),value) for name, value in attrs)

      return type(futer_class_name, future_class_parent, uppercase_attr)

    __metaclass__ = upper_attr

    class Foo(object):

      bar = 'bip'

    print(hasattr(Foo, 'bar'))

    print(hasattr(Foo, 'BAR'))

    f = Foo()

    print(hasattr(f,'bar'))

    print(hasattr(f,'BAR'))

     

    关于Python2对__metaclass__的跟详细的解释请看:

    http://blog.jobbole.com/21351/               -------------python2中__metaclass__的用法
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  • 原文地址:https://www.cnblogs.com/qingsheng/p/9635313.html
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