Turtle库

下列turtle库的简单常用指令

forward(distance) #将箭头移到某一指定坐标

left(angel)　　right(angel)

penup() #提起笔，用于另起一个地方绘制时用，与pendown()配对使用

goto(x,y)

home()

circle(radius)

speed()

 #五角星图形
 from turtle import Turtle

 p = Turtle()
 p.speed(3)
 p.pensize(5)
 p.color("black", 'yellow')
 #p.fillcolor("red")
 p.begin_fill()
 for i in range(5):
     p.forward(200)  #将箭头移到某一指定坐标
     p.right(144)    #当前方向上向右转动角度
 p.end_fill()

树的绘制

观察：对称树， 从主杆出发以一定角度向左向右生成对称的枝丫， 且每一棵枝杈上以相同的角度生成更小的左右枝杈，如此往复。

　　　　联系：所学内容，易想到利用递归程序实现；

 # 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.getscreen().tracer(10,0)
         #Return the TurtleScreen object the turtle is drawing on.
         #TurtleScreen methods can then be called for that object.
     #p.speed(10)
     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()

森林的绘制 

如何画出多棵树，甚至整片森林呢？

答案很简单，只要在画每棵树之前调整画笔的位置，调用画树程序，就可以从新位置生成一颗新树了。

利用模块化的函数思想，调整代码：

将每棵树的绘制以maketree函数封装，参数x,y为画树的起点位置即树根位置。在main函数中只要以

　不同的参数设置来调用maketree函数就可以完成多棵树的绘制了

 # 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 maketree(x, y):
     p = Turtle()
     p.color("green")
     p.pensize(5)
     p.hideturtle()
     p.getscreen().tracer(30, 0)
     p.left(90)

     p.penup()
     p.goto(x, y)
     p.pendown()

     t = tree([p], 110, 65, 0.6375)
     print(len(p.getscreen().turtles())) #用了多少个turtle绘制

 def main():
     maketree(-200, -200)
     maketree(0, 0)
     maketree(200, -200)

 main()

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