Plotting Moving Average in Matplotlib

Question

I've done some research, but i don't really understand how MA is made. I have this plot:

but I really want something like this:

my code is quite simple ( loss[20:] is the list from which want I to do the Moving Average):

plt.figure(figsize=(10, 7))
plt.plot(acc[20:])
plt.plot(loss[20:])
plt.xticks(np.arange(0, len(X) + 200, 500))
plt.show()

I would really appreciate some explanation about this.