import matplotlib.pyplot as plt
import numpy as np
import scipy as sci

xdata = np.linspace(-1, 1, 50)  # [-1;1] échantilloné sur 50 valeurs
ydata = np.array(np.random.uniform(17, 20, 50))  # 50 valeurs au hasard entre -2 et 2

fig, ax = plt.subplots()

ax.set_title('premier exemple')
ax.set_xlabel(' x axis')
ax.set_ylabel(' y axis')

ax2 = ax.twinx()
ax.plot(xdata, ydata, label='sample data')
ax2.plot(xdata, 3 * xdata ** 2, label='quadratic', color='red')
ax2.spines['right'].set_color('red')
ax2.tick_params(axis='y', colors='red')
fig.legend()

plt.show()