Turtle庫

下列turtle庫的簡單常用指令

forward(distance) #將箭頭移到某一指定坐標 

left(angel)　　right(angel) 

penup() #提起筆，用於另起一個地方繪制時用，與pendown()配對使用 

goto(x,y) 

home() 

circle(radius) 

speed() 

#五角星圖形
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)  #將箭頭移到某一指定坐標 
    p.right(144)    #當前方向上向右轉動角度
p.end_fill()

樹的繪制 

觀察：對稱樹， 從主桿出發以一定角度向左向右生成對稱的枝丫， 且每一棵枝杈上以相同的角度生成更小的左右枝杈，如此往復。

　　　　聯系：所學內容，易想到利用遞歸程序實現； 

 

# 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.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 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()

 

森林的繪制 

如何畫出多棵樹，甚至整片森林呢？ 

答案很簡單，只要在畫每棵樹之前調整畫筆的位置，調用畫樹程序，就可以從新位置生成一顆新樹了。 

利用模塊化的函數思想，調整代碼： 

將每棵樹的繪制以maketree函數封裝，參數x,y為畫樹的起點位置即樹根位置。在main函數中只要以

　不同的參數設置來調用maketree函數就可以完成多棵樹的繪制了 

 

# 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 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())) #用了多少個turtle繪制

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

main()

 

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