national flag

# -*- coding：UTF-8 -*-
# -*- author：deng -*-
import turtle
import math
window = turtle.Screen()
def draw_polygon(aTurtle, size=50, n=3):
    # 绘制正多边形
    for i in xrange(n):
        aTurtle.forward(size)
        aTurtle.left(360.0 / n)

def draw_n_angle(aTurtle, size=50, num=5, color=None):
    # 绘制正n角形，默认为黄色
    if color:
        aTurtle.begin_fill()
        aTurtle.fillcolor(color)
    for i in range(num):
        aTurtle.forward(size)
        aTurtle.left(360.0 / num)
        aTurtle.forward(size)
        aTurtle.right(2 * 360.0 / num)
    if color:
        aTurtle.end_fill()

def draw_5_angle(aTurtle=None, start_pos=(0, 0), end_pos=(0, 10), radius=100, color=None):
    #根据起始位置、结束位置和外接圆半径画五角星
    aTurtle = aTurtle or turtle.Turtle()
    size = radius * math.sin(math.pi / 5) / math.sin(math.pi * 2 / 5)
    aTurtle.left(math.degrees(math.atan2(end_pos[1] - start_pos[1], end_pos[0] - start_pos[0])))
    aTurtle.penup()
    aTurtle.goto(start_pos)
    aTurtle.fd(radius)
    aTurtle.pendown()
    aTurtle.right(math.degrees(math.pi * 9 / 10))
    draw_n_angle(aTurtle, size, 5, color)

def draw_5_star_flag(times=20.0):
    #绘制五星红旗
    width, height = 30 * times, 20 * times
    # 初始化屏幕和海龟
    aTurtle = turtle.Turtle()
    aTurtle.hideturtle()
    aTurtle.speed(10)
    # 画红旗
    aTurtle.penup()
    aTurtle.goto(-width / 2, height / 2)
    aTurtle.pendown()
    aTurtle.begin_fill()
    aTurtle.fillcolor('red')
    aTurtle.fd(width)
    aTurtle.right(90)
    aTurtle.fd(height)
    aTurtle.right(90)
    aTurtle.fd(width)
    aTurtle.right(90)
    aTurtle.fd(height)
    aTurtle.right(90)
    aTurtle.end_fill()
    # 画大星星
    draw_5_angle(aTurtle, start_pos=(-10 * times, 5 * times), end_pos=(-10 * times, 8 * times), radius=3 * times,
                 color='yellow')
    # 画四个小星星
    stars_start_pos = [(-5, 8), (-3, 6), (-3, 3), (-5, 1)]
    for pos in stars_start_pos:
        draw_5_angle(aTurtle, start_pos=(pos[0] * times, pos[1] * times), end_pos=(-10 * times, 5 * times),
                     radius=1 * times, color='yellow')

    window.exitonclick()


if __name__ == '__main__':
    draw_5_star_flag()
    turtle.deno()