python画树#函数与递归

    # drawtree.py
     
    from turtle import Turtle, mainloop
     
    def tree(plist, l, a, f):
        """ plist is list of pens
        l is length of branch
        a is half of the angle between 2 branches
        f is factor by which branch is shortened
        from level to level."""
        if l > 5: #
            lst = []
            for p in plist:
                p.forward(l)#沿着当前的方向画画Move the turtle forward by the specified distance, in the direction the turtle is headed.
                q = p.clone()#Create and return a clone of the turtle with same position, heading and turtle properties.
                p.left(a) #Turn turtle left by angle units
                q.right(a)# turn turtle right by angle units, nits are by default degrees, but can be set via the degrees() and radians() functions.
                lst.append(p)#将元素增加到列表的最后
                lst.append(q)
            tree(lst, l*f, a, f)
       
                
     
    def main():
        p = Turtle()
        p.color("green")
        p.pensize(5)
        #p.setundobuffer(None)
        p.hideturtle() #Make the turtle invisible. It’s a good idea to do this while you’re in the middle of doing some complex drawing,
        #because hiding the turtle speeds up the drawing observably.
        #p.speed(10)
       # p.getscreen().tracer(1,0)#Return the TurtleScreen object the turtle is drawing on.
        p.speed(10)
        #TurtleScreen methods can then be called for that object.
        p.left(90)# Turn turtle left by angle units. direction 调整画笔
     
        p.penup() #Pull the pen up – no drawing when moving.
        p.goto(0,-200)#Move turtle to an absolute position. If the pen is down, draw line. Do not change the turtle’s orientation.
        p.pendown()# Pull the pen down – drawing when moving. 这三条语句是一个组合相当于先把笔收起来再移动到指定位置，再把笔放下开始画
        #否则turtle一移动就会自动的把线画出来
     
        #t = tree([p], 200, 65, 0.6375)
        t = tree([p], 200, 65, 0.6375)
         
    main()

转载于:https://www.cnblogs.com/EXODUS1917/p/7232749.html