画图

import numpy as np
import matplotlib.pyplot as plt
x=np.linspace(0,6,100)
y=np.cos(2*np.pi*x)*np.exp(-x)+0.8
plt.plot(x,y,'k',color='r',linewidth=3,linestyle='-')
plt.show()

　　

import matplotlib.pyplot as plt
import numpy as np
x=np.linspace(0,6,100)
y=np.cos(2*np.pi*x)*np.exp(-x)+0.8
plt.plot(x,y,'k',color='r',label='27',linewidth=3)
plt.axis([0,6,0,1.8])
ix=(x>0.8) & (x<3)
plt.fill_between(x,y,0,where=ix,\
                 facecolor='grey',alpha=0.25)
plt.text(0.5*(0.8+3),0.2,r"$\int_a^b f(x)\mathrm{d}x$",\
         horizontalalignment='center')
plt.legend()
plt.show()