通过类中的定义引用用户生成的类对象的附加列表？

Question

我想创建一个类

Ball

，并创建用户为该类生成的对象列表。然后，我将在

run()

中引用此列表，以在

pygame

中绘制用户生成的对象。我的问题如下：

当我尝试引用

Ball(a, v, r...)

时，它说

Ball

在我的定义之前被引用。如有任何帮助，我们将不胜感激！

这里是完整的错误： 文件“/Users/.../Desktop/.../python/promot.py”，第 66 行，运行中 balls.append(Ball(a, v, r, c, x_pos, y_pos)) #这里我得到错误 ^^^^ UnboundLocalError：无法访问未与值关联的局部变量“Ball”

import pygame
import math
 
pygame.init()
 
#screen
framespd = 30 #what is frame speed for gravity = 9.81
gravity = 1
t = 0.01
clock = pygame.time.Clock()
width, height = 1000, 1000
pygame.display.set_caption("Orbit Take 1")
screen = pygame.display.set_mode([width, height])
 
class Ball:
    def __init__(self, angle, velocity, radius, color, x_pos, y_pos):
        self.angle = angle
        self.velocity = velocity
        self.radius = radius
        self.color = color
        self.x_pos = x_pos
        self.y_pos = y_pos
 
    def draw(self):
        self.circle = pygame.draw.circle(screen, self.color, (self.x_pos, self.y_pos), self.radius)
 
    def true_velocity_x(self):
        true_velocity_x = self.velocity * math.cos(self.angle)
 
    def true_velocity_y(self):
        true_velocity_y = self.velocity * math.sin(self.angle)
        new_velocity_y = true_velocity_y + (gravity * t)
 
    #def update position(self):
        #x pos = x velocity
        #y pos += y velocity
 
balls = [] 
 
def run():
    value = True
    while value:
        clock.tick(framespd)
 
        # Balls in sim
 
        number_balls = int(input("How many balls: "))
 
        while len(balls) < number_balls:
            # Variables for Ball
            a = input("Angle: ")
            v = input("Velocity: ")
            r = input("Radius: ")
            c = input("Color: ")
            x_pos = '0'
            y_pos = '500'
            balls.append(Ball(a, v, r, c, x_pos, y_pos)) #here i get error "local variable "Ball" defined in enclosing scope on line 24 referenced before assignment"
 
        screen.fill('black')    
 
        #draw ball
        for Ball in balls:
            Ball.draw(pygame.display.set_mode((width, height)))
        #update position
 
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                value = False
            pygame.display.flip()
    pygame.quit()       
 
run()

我的第一次尝试以粗体引用为“我尝试过的其他东西”，但我在使用初始化之外的类时遇到了麻烦，没有错误。我的下一次尝试是“当前尝试”，当我运行时没有显示任何内容。

Answer 1

import pygame
import math

pygame.init()

# screen
framespd = 30  # what is frame speed for gravity = 9.81
gravity = 1
t = 0.01
clock = pygame.time.Clock()
width, height = 1000, 1000
pygame.display.set_caption("Orbit Take 1")
screen = pygame.display.set_mode([width, height])


class Ball:
    def __init__(self, angle, velocity, radius, color, x_pos, y_pos):
        self.angle = angle
        self.velocity = velocity
        self.radius = radius
        self.color = color
        self.x_pos = x_pos
        self.y_pos = y_pos

    def draw(self):
        self.circle = pygame.draw.circle(screen, self.color, (self.x_pos, self.y_pos), self.radius)

    def true_velocity_x(self):
        true_velocity_x = self.velocity * math.cos(self.angle)

    def true_velocity_y(self):
        true_velocity_y = self.velocity * math.sin(self.angle)
        new_velocity_y = true_velocity_y + (gravity * t)

    # def update position(self):
    # x pos = x velocity
    # y pos += y velocity


balls = []


def run(cls = Ball):
    value = True
    while value:
        clock.tick(framespd)

        # Balls in sim

        number_balls = int(input("How many balls: "))

        while len(balls) < number_balls:
            # Variables for Ball
            a = input("Angle: ")
            v = input("Velocity: ")
            r = input("Radius: ")
            c = input("Color: ")
            x_pos = '0'
            y_pos = '500'
            balls.append(cls(a, v, r, c, x_pos,
                              y_pos))  # here i get error "local variable "Ball" defined in enclosing scope on line 24 referenced before assignment"

        screen.fill('black')

        # draw ball
        for Ball in balls:
            Ball.draw(pygame.display.set_mode((width, height)))
        # update position

        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                value = False
            pygame.display.flip()
    pygame.quit()


run()