how to add legend to python plot

1import numpy as np
2import matplotlib.pyplot as plt
3
4x = np.linspace(0, 20, 1000)
5y1 = np.sin(x)
6y2 = np.cos(x)
7
8plt.plot(x, y1, "-b", label="sine")
9plt.plot(x, y2, "-r", label="cosine")
10plt.legend(loc="upper left")
11plt.ylim(-1.5, 2.0)
12plt.show()
13

1plt.legend(['first', 'second']);