Python:运算符重载特定类型

def __add__(self, other):
    if isinstance(other, self.__class__):
        return self.x + other.x
    elif isinstance(other, int):
        return self.x + other
    else:
        raise TypeError("unsupported operand type(s) for +: '{}' and '{}'").format(self.__class__, type(other))

class Mynum(object):
    def __init__(self, x):
        self.x = x
    def __add__(self, other):
        try:
            return self.x + other.x
        except AttributeError:
            return self.x + other
    __radd__=__add__

a = Mynum(1)
b = Mynum(2)

print(a+b)
# 3
print(a+2)
# 3
print(2+a)
# 3

为什么要使用额外的切换和/或异常处理?使用以下方法更简单:

class MyNum(object):
    def __init__(self, x):
        self.x = x
    def __add__(self, other):
        return other + self.x
    __radd__ = __add__
x = MyNum(5)
y = MyNum(6)
print x + 2
7
print 2 + x
7
print x + y
11
print y + x
11