如何在matplotlib中首先绘制线条并最后绘制点

我有一个简单的绘图，其中包含多组点和线，每组点和线连接在一起.我希望将点绘制在线条的顶部(这样线条就不会显示在该点的内部).不管plot和scatter调用的顺序如何，此图都一样，而不是我想要的.有简单的方法吗?

I have a simple plot with several sets of points and lines connecting each set. I want the points to be plotted on top of the lines (so that the line doesn't show inside the point). Regardless of order of the plot and scatter calls, this plot comes out the same, and not as I'd like. Is there a simple way to do it?

import math
import matplotlib.pyplot as plt

def poisson(m):
    def f(k):
        e = math.e**(-m)
        f = math.factorial(k)
        g = m**k
        return g*e/f
    return f

R = range(20)
L = list()
means = (1,4,10)
for m in means:
    f = poisson(m)
    L.append([f(k) for k in R])
colors = ['r','b','purple']

for c,P in zip(colors,L):
    plt.plot(R,P,color='0.2',lw=1.5)
    plt.scatter(R,P,s=150,color=c)

ax = plt.axes()
ax.set_xlim(-0.5,20)
ax.set_ylim(-0.01,0.4)
plt.savefig('example.png')