2.对前面的代码进行优化，用for,while,if,def实现：

(1).画五角星

import turtle
for i in range(5):
 turtle.forward(100)
 turtle.right(144)

如图所示：

(2).画同心圆

import turtle
for i in range(5):
turtle.up()
turtle.goto(0,-20*(i+1))
turtle.down()
turtle.circle(20*(i+1))

如图所示：

(3).画太阳花

import turtle

turtle.color('yellow','red')
turtle.begin_fill()
while True:
turtle.forward(200)
turtle.left(150)
if (abs(turtle.pos()))<1:
    break
turtle.end_fill()
done()

如图所示：

(4).画五个角星

import turtle
turtle.setup(600,400,0,0)
turtle.bgcolor('red')
turtle.color('yellow')
turtle.fillcolor('yellow')
def mygoto(x,y):
    turtle.up()
    turtle.goto(x,y)
    turtle.down()
mygoto(-250,75)
turtle.begin_fill()
for i in range(5):
    turtle.forward(120)
    turtle.right(144)
turtle.end_fill()
mygoto(-70,120)
turtle.begin_fill()
for i in range(5):
    turtle.forward(-30)
    turtle.right(144)
turtle.end_fill()
mygoto(-30,80)
turtle.begin_fill()
for i in range(5):
    turtle.forward(-30)
    turtle.right(144)
turtle.end_fill()
mygoto(-35,30)
turtle.begin_fill()
for i in range(5):
    turtle.forward(-30)
    turtle.left(144)
turtle.end_fill()
mygoto(-70,-25)
turtle.begin_fill()
for i in range(5):
    turtle.forward(-30)
    turtle.right(144)
turtle.end_fill()

如图所示：