# 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)#沿着當前的方向畫畫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)#將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 調整畫筆 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. 這三條語句是一個組合相當於先把筆收起來再移動到指定位置，再把筆放下開始畫 #否則turtle一移動就會自動的把線畫出來 #t = tree([p], 200, 65, 0.6375) t = tree([p], 200, 65, 0.6375) main()
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