Python类属性和子类化

我已经在谷歌上搜索和玩了一段时间，但尝试这样做没有结果：

class  A(object):
    cl_att = 'I am an A class attribute'

class  B(A):
    cl_att += ' modified for B type'

class  C(A):
    cl_att += ' modified for C type'


instA = A()
print insAt.cl_att
>>> I am an A class attribute

instB = B()
print instB.cl_att
>>> I am an A class attribute modified for B type

instC = C()
print instC.cl_att
>>> I am an A class attribute modified for C type

print instA.cl_att
>>> I am an A class attribute

class  A(object):
    cl_att = 'I am an A class attribute'

@inherit_and_append('cl_att')
class  B(A):
    cl_att = ' modified for B type'

@inherit_and_append('cl_att')
class  C(A):
    cl_att = ' modified for C type'

---

简而言之，我希望能够“使用并覆盖”父类中的类属性。

引用父类属性并连接到它：

class  A(object):
    cl_att = 'I am an A class attribute'

class  B(A):
    cl_att = A.cl_att + ' modified for B type'

class  C(A):
    cl_att = A.cl_att + ' modified for C type'

类主体的执行与函数非常相似，局部名称构成类属性

cl_att

不存在于新的“函数”中，用于创建

B

和

C

的主体，因此您需要直接引用基类上的属性

演示：

---

假设您只有一个父类，您可以使用子类答案末尾定义的

inherit\u和\u append

decorator来获得所需的结果，如下所示：

class  A(object):
    cl_att = 'I am an A class attribute'

class  B(A):
    cl_att += ' modified for B type'

class  C(A):
    cl_att += ' modified for C type'


instA = A()
print insAt.cl_att
>>> I am an A class attribute

instB = B()
print instB.cl_att
>>> I am an A class attribute modified for B type

instC = C()
print instC.cl_att
>>> I am an A class attribute modified for C type

print instA.cl_att
>>> I am an A class attribute

class  A(object):
    cl_att = 'I am an A class attribute'

@inherit_and_append('cl_att')
class  B(A):
    cl_att = ' modified for B type'

@inherit_and_append('cl_att')
class  C(A):
    cl_att = ' modified for C type'

如果有更高级的要求或条件，您可以进一步扩展decorator

class inherit_and_append(object):
    def __init__(self, *attrs):
        super(inherit_and_append, self).__init__()

        self._attrs = attrs

    def __call__(self, klass):
        parent = klass.__bases__[0]  # Assuming you have a single parent class
        for attr in self._attrs:
            if not hasattr(parent, attr):
                raise AttributeError("'{}' class has no '{}' attribute".format(parent.__name__, attr))

            parent_value = getattr(parent, attr)
            klass_value = getattr(klass, attr)
            setattr(klass, attr, parent_value + klass_value)

        return klass