Pygame 绘制弧形

import pygame,sys,math
from pygame.locals import *
pygame.init()
screen = pygame.display.set_mode((600,500))
pygame.display.set_caption("Drawing Arcs")
while True:
    for event in pygame.event.get():
        if event.type in (KEYDOWN,QUIT):
            sys.exit()
    screen.fill((255,255,255))
    color = 100,255,100
    position = 200,150,200,200
    start_angle = math.radians(0)
    end_angle = math.radians(180)
    width = 5
    pygame.draw.arc(screen,color,position,start_angle,end_angle,width)
    pygame.display.update()