2.使用turtle库画一组同心圆

'''方法一
from turtle import *
setup(600,400,500,200)
color("red")
pensize(2)
circle(20)
for i in range(1,4):
    penup()
    goto(0,-10*i)
    pendown()
    circle(20+i*10)
hideturtle()
done()'''

#方法二
import turtle
turtle.setup(600,400,500,200)
turtle.color("red")
turtle.pensize(2)
turtle.circle(20)
for i in range(1,4):
    turtle.penup()
    turtle.goto(0,-10*i)
    turtle.pendown()
    turtle.circle(20+i*10)
turtle.hideturtle()
turtle.done()