函数递归 案例一 分形树

import turtle

这里的 turtle 绘画库 
https://www.cnblogs.com/kwkk978113/p/10307013.html

def draw_brach(brach_length):
　　　　""" 递归函数进行画分形树 """
    if brach_length > 5:
        turtle.pencolor("brown")
        turtle.pensize(3)
        turtle.forward(brach_length)
        turtle.right(30)
        draw_brach(brach_length - 15)

        turtle.left(60)
        draw_brach(brach_length - 15)

        turtle.right(30)
        turtle.up()
        turtle.backward(brach_length)
        turtle.down()
        if brach_length<=10:
            turtle.pencolor("green")
            turtle.pensize(5)
            turtle.forward(brach_length)
            turtle.right(30)
            draw_brach(brach_length - 15)

            turtle.left(60)
            draw_brach(brach_length - 15)

            turtle.right(30)
            turtle.up()
            turtle.backward(brach_length)
            turtle.down()


def main():
    turtle.speed(100)
    turtle.left(90)
    turtle.up()
    turtle.backward(200)
    turtle.down()
    turtle.pensize(10)
    draw_brach(100)

    turtle.exitonclick()
if __name__ == ‘__main__‘:
    main()