绘制同心圆

从键盘输入半径、绘制同心圆的个数及画笔的颜色

import turtle

turtle.pensize(10)

r=eval(input())
n=eval(input())
color=input()
turtle.pencolor(color)

for i in range(n):
    turtle.circle(r+(i-1)*20,360)#每个同心圆的半径差为20
    turtle.penup()
    turtle.right(90)
    turtle.forward(20)
    turtle.left(90)
    turtle.pendown()

键盘输入：

                    20

                    4

                    red