EG 1
import numpy as np
import matplotlib.pyplot as plt
y = np.arange(1, 5)
plt.plot(y, y + 2, label='Normal')
plt.plot(y, y + 3, label='Fast')
plt.plot(y, y + 4, label='Faster')
plt.legend() # hasn't this , can't show
plt.legend(['2','3','4']) # repeat set , will repace
plt.show()