plot filled circles (a donut) with matplotlib

# -*- coding: utf-8 -*-
"""
Created on Fri Apr 20 19:47:38 2018
plot filled circles (a donut) with matplotlib
"""
import numpy as np
import matplotlib.pyplot as plt
import math


def plot_circle_donut(pos, inner, outer, color):
    """
     REF: https://stackoverflow.com/questions/22789356/plot-a-donut-with-fill-or-fill-between-use-pyplot-in-matplotlib
     ton10's answer
    """
    x = np.linspace(-outer, outer, 300, endpoint=True)

    yO = outer * np.sin(np.arccos(x/ outer )) # x-axis values -> outer circle
    yI = inner * np.sin(np.arccos(x/ inner )) # x-axis values -> inner circle (with nan's beyond circle)
    yI[np.isnan(yI)] = 0.                 # yI now looks like a boulder hat, meeting yO at the outer points

    ax = plt.subplot(111)
    ax.fill_between(x+pos[0], yI+pos[1], yO+pos[1], color=color)
    ax.fill_between(x+pos[0], -yO+pos[1], -yI+pos[1], color=color)

    plt.show()
#

def plot_circle(r, pos):
    """ REF: https://math.stackexchange.com/questions/260096/find-the-coordinates-of-a-point-on-a-circle """
    arrx = []
    arry = []
    for theta in xrange(1000):
        x,y = r * math.sin(theta), r * math.cos(theta)
        arrx.append(x)
        arry.append(y)
    #
    plt.plot(arrx, arry, color='red')

    plt.show()
#


#r = 3
#pos = 2,2
#plot_circle(r, pos)

r1, r2 = 2, 2.1
position = [4,2]
color = 'b'
plot_circle_donut(position, r1, r2, color)