save project

my_tree.py

 import turtle
+import random
 turtle.speed(0)
 def tree(n):
     if n>=0:
-        turtle.forward(n)
-        turtle.right(30)
-        tree(n-10)
-        turtle.left(60)
-        tree(n-10)
-        turtle.right(30)
-        turtle.up()
-        turtle.forward(-n) 
-        turtle.down()
-
+        if n <= 12 :
+            color_list = ['snow','lightcoral']
+            color  =random.choice(color_list)
+            pen.color(color)
+            pen.pensize(n/3)
+        else:
+            pen.color('sienna')
+            pen.pensize(n/10)
+        pen.forward(n)
+        angle = random.random()
+        pen.right(30*angle)
+        length = 1.5*random.random()
+        tree(n-10*length)
+        pen.left(60*angle)
+        tree(n-10*length)
+        pen.right(30*angle)
+        pen.up()
+        pen.backward(n) 
+        pen.down()
 
 pen = turtle.Turtle()
 pen.color('sienna')
@@ -20,10 +30,10 @@ w = turtle.Screen()
 w.bgcolor('wheat')      # wheat小麦
 
 # 移动到起点
-turtle.left(90)
-turtle.up()
-turtle.backward(150)
-turtle.down()
+pen.left(90)
+pen.up()
+pen.backward(150)
+pen.down()
 
 tree(60)
 turtle.done()