import matplotlib.pyplot as plt
import numpy as np

P = np.linspace(-5,5,40)
Eg = 10
E1 = -0.5*P**2
E2 = Eg+P**2
figure = plt.figure(figsize = (3.5,5))
plt.plot(P,E1,color = "k")
plt.plot(P,E2,color = "k")
plt.plot(P,E1,"o",color = "blue")



P1 = 2
P2 = 2

plt.plot(P[abs(P)<P1],E1[abs(P)<P1], "o",color = "red", markersize = 9)

plt.plot(P[abs(P)<P1],E1[abs(P)<P1], "o",color = "white")

plt.plot(P[abs(P)<P2],E2[abs(P)<P2], "o", color = "blue")

plt.xlim([min(P), max(P)])
plt.ylim([min(E1), max(E2)])

plt.xlabel("Impulsion")
plt.tight_layout()
plt.show()