Python:AttributeError: 'Point'对象没有属性 'x'

Question

Traceback (most recent call last):
line 56, in <module>
    distanceToOne = point1.Distance(pointUser)
line 22, in Distance
    distance = math.sqrt((self.__x - toPoint.x)**2 +(self.__y - toPoint.y)**2 +(self.__z - toPoint.z)**2)
AttributeError: 'Point' object has no attribute 'x'

出于某种原因，每当我获取三个点来计算距离后，每当我到达:distanceToOne = point1.Distance(pointUser) 时，我都会收到上述错误消息。

如果需要的话，这里有一个更好的 View :http://pastie.org/private/vige6oaphkwestdemr5uw

预先感谢您的帮助!

import math
class Point(object):
    def __init__(self, x = 0, y = 0, z = 0, description = 'TBD'):
        self.__x = x
        self.__y = y
        self.__z = z
        self.__description = description

    def SetPoint(self, coords):
        self.__x = coords[0]
        self.__y = coords[1]
        self.__z = coords[2]

    def GetPoint(self):
        return [self.__x, self.__y, self.__z]
    PointCoords = property(GetPoint, SetPoint)

    def Distance(self, toPoint):
        toPoint.PointCoords[0]
        toPoint.PointCoords[1]
        toPoint.PointCoords[2]
        return math.sqrt(
            (self.__x - toPoint.x)**2 +
            (self.__y - toPoint.y)**2 +
            (self.__z - toPoint.z)**2)

    def SetDescription(self, description):
        self.__description = description

    def GetDescription(self):
        return self.__description
    PointDescription = property(GetDescription, SetDescription)

if __name__ == "__main__":
    print "Program 9: Demonstrate how to define a class"

    point2 = Point()
    point1 = Point(10, 54, 788, 'Ploto')
    point2.PointCoords = 77, 2, 205
    point2.PointDescription = 'Mars'
    doAnother = "y"
    while(doAnother == "y"):
        pointX = raw_input("Enter a X Number: ")
        pointY = raw_input("Enter a Y Number: ")
        pointZ = raw_input("Enter a Z Number: ")

        # Constructor - Represent the user's location
        pointUser = Point(pointX, pointY, pointZ, 'Sun')

        distanceToOne = point1.Distance(pointUser)
        distanceToTwo = point2.Distance(pointUser)

        # Comparing the two distances between the two to see which one is the closest
        if (distanceToOne > distanceToTwo):
            closest = point2
        else:
            closest = point1
            print ('You are closest to',closest.PointDescription(), 'which is located at ',closest.PointCoords())
        doAnother = raw_input("Do another (y/n)? ").lower()
    print ('Good Bye!')

Answer 1

实际错误是由于访问 toPoint.x 造成的，该文件不存在，因为您从未定义过它。

相关说明，在属性前面添加双下划线会激活 python name mangling特征。实际属性仍可在类外部的 my_point._Point__x、my_point._Point__y 等处公开访问。

就风格而言，在这种情况下似乎没有任何理由使用名称修饰。此功能的预期用例是避免与继承的类发生冲突，它并不是真正尝试创建“私有(private)”变量(为此，约定是使用单个下划线来指示属性何时为实现细节)。

就你的情况而言，我认为你应该正常命名(和访问)属性 x、y 等。在 python 中，我们通常不编写 getters 和类成员的 setter ，除非有特殊要求，因为 Python is not Java 。