如何用python画一个圆？用什么函数来绘制？

from matplotlib.patches import Ellipse, Circle
import matplotlib.pyplot as plt

def plot_cicle():
    fig = plt.figure()
    ax = fig.add_subplot(111)

    cir1 = Circle(xy = (0.0, 0.0), radius=2, alpha=0.5)
    ax.add_patch(cir1)

    x, y = 0, 0
    ax.plot(x, y, 'ro')

    plt.axis('scaled')
    plt.axis('equal')   #changes limits of x or y axis so that equal increments of x and y have the same length

    plt.show()
 
plot_cicle()