1 
...
 return cls(P2[0] - P1[0], P2[1] - P1[1])
TypeError: 'Vector' object does not support indexing

我是 pygame 和 python 的新手。我一直在尝试练习构建类和向量，非常挣扎。

这是我的类文件

import math

class Vector(object):

    #defaults are set at 0.0 for x and y
    def __init__(self, x=0.0, y=0.0):
        self.x = x
        self.y = y

    #allows us to return a string for print
    def __str__(self):
        return "(%s, %s)"%(self.x, self.y)

    # from_points generates a vector between 2 pairs of (x,y) coordinates
    @classmethod
    def from_points(cls, P1, P2):
        return cls(P2[0] - P1[0], P2[1] - P1[1])

    #calculate magnitude(distance of the line from points a to points b
    def get_magnitude(self):
        return math.sqrt(self.x**2+self.y**2)

    #normalizes the vector (divides it by a magnitude and finds the direction)
    def normalize(self):
        magnitude = self.get_magnitude()
        self.x/= magnitude
        self.y/= magnitude

    #adds two vectors and returns the results(a new line from start of line ab to end of line bc)
    def __add__(self, rhs):
        return Vector(self.x +rhs.x, self.y+rhs.y)

    #subtracts two vectors
    def __sub__(self, rhs):
        return Vector(self.x - rhs.x, self.y-rhs.y)

    #negates or returns a vector back in the opposite direction
    def __neg__(self):
        return Vector(-self.x, -self.y)

    #multiply the vector (scales its size) multiplying by negative reverses the direction
    def __mul__(self, scalar):
        return Vector(self.x*scalar, self.y*scalar)

    #divides the vector (scales its size down)
    def __div__(self, scalar):
        return Vector(self.x/scalar, self.y/scalar)

    #gives my vector class an ability to return a tuple
    def tuple(self):
        return (self.x, self.y)

这是我的程序代码

#The simple mouse move game by Ramon Cabral


#imports
import pygame, sys, Vector
from pygame.locals import *
from Vector import *

#game init
pygame.init()

#screen
screen = pygame.display.set_mode((800,600),0,32)

#images
mouse_file = 'mouse.png'
MOUSE = pygame.image.load(mouse_file).convert_alpha()


#variables
bgcolor = (255,255,255)
position = Vector(100.0,100.0)
heading = Vector()

#clock and speed
clock = pygame.time.Clock()
speed = 250.0


#main game function
while True:

    for event in pygame.event.get():
        if event.type == QUIT:
            pygame.quit()

        if event.type == MOUSEBUTTONDOWN:
            destination = pygame.mouse.get_pos()
            heading = Vector.from_points(position, destination)
            heading.normalize()

    screen.fill(bgcolor)
    screen.blit(MOUSE, position.tuple())

    time_passed = clock.tick(30.)
    time_passed_seconds = time_passed/1000.0

    distance_moved = time_passed_seconds*speed
    position += heading * distance_moved
    pygame.display.update()
4

1 回答 1

1

它应该是：

@classmethod
def from_points(cls, P1, P2):
    return cls(P2.x - P1.x, P2.y - P1.y)

原因是你的类没有__getitem__方法，所以你不能索引它：

P2[0]  #not allowed since this calls `__getitem__` and your class doesn't define it.
于 2013-02-28T06:01:09.380 回答