爲什麼我的pygame球在使用類時不會加速？

Question

所以我是新來的pygame/python /編碼和第一次使用類。我已經做出了一個工作pygame程序的球彈跳和重力加速。但是，現在我使用了課堂，球只似乎以恆定的速度移動。請告訴我我做錯了什麼，以及如何改變我的代碼。提前致謝！

import pygame, sys 


pygame.init() 

red = (255,0,0) 
black = (0,0,0) 
white = (255,255,255) 
blue = (0,0,255) 

pygame.mouse.set_visible(0) 
clock = pygame.time.Clock() 

displaySize = (800,600) 

screen = pygame.display.set_mode(displaySize) 

g = 30 
dt = 0.05 

class ball: 
    def __init__(self, x, y, vx, vy, r,ax,ay, color): 

     dt = 0.05 

     Cd = 0.01 
     m = 5 

     self.ay = ay 
     self.ax = ax 

     self.x = x 
     self.y = y 
     self.r = r 
     self.color = color 

     self.vx = vx 
     self.vy = vx 

def update(self, x, y): 


    x, y = physics() 
    pygame.draw.circle(screen, self.color, (int(round(x)),int(round(y))), self.r) 
    pygame.display.update() 

    def physics(self): 


     self.Dy = Cd*self.vy*abs(self.vy) 
     self.Dx = Cd*self.vx*abs(self.vx) 

     self.Fy = self.m*g - self.Dy 
     self.Fx = -self.Dx 

     self.ay = self.Fy/m 
     self.ax = self.Fx/m 

     self.vy += self.ay*dt 
     self.vx += self.ax*dt 

     self.x +=self.vx*dt 
     self.y +=self.vy*dt 

     return self.x, self.y 

one = ball(100,100,0,0,0,0,30,red) 

while 1: 
    clock.tick(30) 
    screen.fill(blue) 
    one.update() 

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

Answer 1

self.vx和self.vy應的構造方法，而不是物理方法之內，否則它們的值將被設置回至50和0每次物理方法被稱爲遊戲循環內，導致以恆定的速度。