import numpy as np from scipy.integrate import odeint import matplotlib.pyplot as plt def diff_equation(y_list,x): y,z=y_list return np.array([z,-y]) x=np.linspace(0,np.pi*2,num=100) y0=[1,1]#y(0)=1,y'(0)=1 result=odeint(diff_equation,y0,x) plt.plot(x,result[:,0],label="y") plt.plot(x,result[:,1],label="z") plt.legend() plt.grid() plt.show()