14pygame贪吃球的思路（如何检测碰撞与删除时报错的分析）

# coding=utf-8 
# Time    : 2018/7/30 16:40
# Author  : 云水君
# Email   : 632942444@qq.com
# File    : 多个球运动.py
# Software: PyCharm

import pygame
from random import randint


def draw_ball(place, color, pos):
    pygame.draw.circle(place, color, pos, 20)
    
    
def collision(pos1, pos2, r1, r2):  # 碰撞检测
    x1, y1 = pos1
    x2, y2 = pos2
    if (x1-x2)**2 + (y1-y2)**2 <= (r1+r2)**2:
        return True
    return False


def abs(n):  # 取绝对值
    if n >= 0:
        return n
    else:
        return -n


if __name__ == '__main__':
    pygame.init()
    screen = pygame.display.set_mode((600, 400))
    pygame.display.set_caption("多个球移动")
    screen.fill((255, 255, 255))
    pygame.display.flip()
    # 初始求的信息
    balls = [{"r": randint(10, 25),   
                   "pos": (100, 100),
                   "color": (randint(0, 253), randint(1, 253), randint(1, 253)),
                   "x_speed": randint(-2, 2),
                   "y_speed": randint(-2, 2)}]
    while True:
        pygame.time.delay(10)
        screen.fill((255, 255, 255))
        index = 0
        balls_temp = []
        for ball_dict in balls[:]:  # 将第一个球 从列表中取出来
            r = ball_dict["r"]
            color = ball_dict["color"]
            x, y = ball_dict["pos"]
            x_speed = ball_dict["x_speed"]
            y_speed = ball_dict["y_speed"]
            balls_temp.append(ball_dict)  # 将已经取出的第一个球存入一个临时列表
            for ball_dict2 in balls[:]:   # 将第二个球从列表中取出来
                if ball_dict2 not in balls_temp:  # 判断第二球有没有在第一次循环中被取出。
                    pos2 = ball_dict2["pos"]
                    r2 = ball_dict2["r"]
                    if collision((x, y), pos2, r, r2):  # 如果发生碰撞 删除掉半径小的球
                        print("碰撞到一起了")
                        if r2 <= r:
                            balls.remove(ball_dict2)
                            ball_dict["r"] = int((r2**2 + r**2)**0.5)
                        else:
                            balls.remove(ball_dict)  # 如果第一个球是小球，就把第一个球删除掉
                            ball_dict2["r"] = int((r2**2 + r**2)**0.5)
                            break    # 此处是重点！把第一个球删除掉后，一定要退出当前循环，不然后面如果还要删除这个球，就会出错！！！
                     
            if x + r >= 600:  # 边界检测
                x_speed = -abs(x_speed)  # 边界检测满足条件，改变速度一定要用绝对值，不然球会在边界来回震动！
            if x - r <= 0:
                x_speed = abs(x_speed)
            if y + r >= 400:
                y_speed = -abs(y_speed)
            if y - r <= 0:
                y_speed = abs(y_speed)
            x += x_speed; y += y_speed
            pygame.draw.circle(screen, color, (x, y), r)
            index += 1
            ball_dict["pos"] = (x, y)
            ball_dict["x_speed"] = x_speed
            ball_dict["y_speed"] = y_speed
        pygame.display.update()

        for event in pygame.event.get():  # 每次循环检测有没有事件发生

            if event.type == pygame.MOUSEBUTTONDOWN:  # 每按一次鼠标 产生一个新的球
                balls.append(
                {"r": randint(10, 25),
                 "pos": event.pos,
                 "color": (randint(1, 253), randint(1, 254), randint(1, 253)),
                 "x_speed": randint(-2, 2),
                 "y_speed": randint(-2, 2)
                 })
            if event.type == pygame.QUIT:  
                exit()