add turtle sample

samples/gui/turtle/rect.py

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+# 导入turtle包的所有内容:
+from turtle import *
+
+# 设置笔刷宽度:
+width(4)
+
+# 前进:
+forward(200)
+# 右转90度:
+right(90)
+
+# 笔刷颜色:
+pencolor('red')
+forward(100)
+right(90)
+
+pencolor('green')
+forward(200)
+right(90)
+
+pencolor('blue')
+forward(100)
+right(90)
+
+# 调用done()使得窗口等待被关闭，否则将立刻关闭窗口:
+done()

samples/gui/turtle/stars.py

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+from turtle import *
+
+def drawStar(x, y):
+    pu()
+    goto(x, y)
+    pd()
+    # set heading: 0
+    seth(0)
+    for i in range(5):
+        fd(40)
+        rt(144)
+
+for x in range(0, 250, 50):
+    drawStar(x, 0)
+
+done()

samples/gui/turtle/tree.py

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+from turtle import *
+
+colormode(255)
+
+lt(90)
+
+lv = 14
+l = 120
+s = 45
+
+width(lv)
+
+r = 0
+g = 0
+b = 0
+pencolor(r, g, b)
+
+penup()
+bk(l)
+pendown()
+fd(l)
+
+def draw_tree(l, level):
+    global r, g, b
+    # save the current pen width
+    w = width()
+
+    # narrow the pen width
+    width(w * 3.0 / 4.0)
+    # set color:
+    r = r + 1
+    g = g + 2
+    b = b + 3
+    pencolor(r % 200, g % 200, b % 200)
+
+    l = 3.0 / 4.0 * l
+
+    lt(s)
+    fd(l)
+
+    if level < lv:
+        draw_tree(l, level + 1)
+    bk(l)
+    rt(2 * s)
+    fd(l)
+
+    if level < lv:
+        draw_tree(l, level + 1)
+    bk(l)
+    lt(s)
+
+    # restore the previous pen width
+    width(w)
+
+speed("fastest")
+
+draw_tree(l, 4)
+
+done()