python drawing four leaf clover

import turtle

def draw_shapes():
    window = turtle.Screen()
    window.bgcolor("red")

    flower = turtle.Turtle()
    flower.speed(10)
    flower.shape("arrow")
    flower.right(45)
    for i in range(1,37):
        for j in range(1,5):
            draw_circle(flower,i,"green")
            flower.left(90)
    flower.right(45)
    flower.color("green")
    flower.forward(500)

    window.exitonclick()

def draw_circle(circle,radius,color):
    circle.color(color)
    circle.circle(radius)

draw_shapes()