Python+Turtle动态绘制一棵树实例分享

# 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()