Question

class Point(object):
    ''' A point on a grid at location x, y '''

    def __init__(self, x, y):
        self.X=x
        self.Y=y   

    def __str__(self):
        return "X=" + str(self.X), "Y=" + str(self.Y)


    def __add__(self, other):
        if not isinstance(other, Point):
            raise TypeError("must be of type point")
        x= self.X+ other.X
        y= self.Y+ other.Y
        return Point(x, y)

p1= Point(5, 8)
print p1 + [10, 12]

当尝试在RHS添加列表或元组时，即打印p1 + [10,12]，我正在

attributeError: int object has no attribute

如何解决这个问题？

Answer 1

首先，我无法重现您显示的确切错误，但我相信这是某种错误＆＃34;＃34;。您正尝试将list实例添加到Point实例，而后者的__add__方法会在您尝试添加非Point的任何内容时抛出错误实例。

def __add__(self, other):
    if not isinstance(other, Point):
        raise TypeError("must be of type point")

你可以通过添加一些相当多的多态来克服它。

from collections import Sequence 


class Point(object):
    ...

    def _add(self, other):
        x = self.X + other.X
        y = self.Y + other.Y
        return Point(x, y)

    def __add__(self, other):
        if isinstance(other, type(self)):
            return self._add(other)
        elif isinstance(other, Sequence) and len(other) == 2:
            return self._add(type(self)(*other))
        raise TypeError("must be of type point or a Sequence of length 2")

Answer 2

您可以使用逗号而不是加号。看看

def __str__(self):
    return "X=" + str(self.X), "Y=" + str(self.Y)

哪个应该是

def __str__(self):
    return "X=" + str(self.X) + ", Y=" + str(self.Y)

至少在python3上，当我更正它时，你的代码运行得很好。显然使用print(p1 + Point(10,12))。

AttributeError：int对象没有属性

2 个答案: