在python中如何画圆？

import turtle      #引进海龟，你可以开始使用它

myColor=["red","green","brown"]

index =0

for x in range(250):

    turtle.pencolor(myColor[index])

    index +=1

    if index == 3:

        index = 0

    turtle.forward(x*2)

    turtle.left(92)