Python 新样式类的运算符

有谁能解释一下为什么

A（）+A（）

确实给出了一个错误，但是

B（）+B（）

工作正常？我在编写一段较大的代码时遇到了这个问题，但这似乎是复制它所需的最小代码

from types import MethodType

D = {'__add__': lambda x, y: "".join((repr(x), repr(y)))}

class A(object):
    def __getattr__(self, item):
        if item == '__coerce__':
            raise AttributeError()
        return MethodType(D[item], self)
    def __repr__(self):
        return "A"

class B():
    def __getattr__(self, item):
        if item == '__coerce__':
            raise AttributeError()
        return MethodType(D[item], self)
    def __repr__(self):
        return "B"

try:
    A()+A()
except Exception as e:
    print e

B()+B()

---

有人对此有什么解释吗？

这是因为新样式的类从不使用二进制运算符调用

\uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu>
。另外，对于特殊方法，
\uuu getattr\uuu
从未在新样式类中调用：从数据模型：

新样式类（从对象派生的样式类）从不调用
\uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu；调用
\uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu