python画log图

import numpy as np
import math
import matplotlib.pyplot as plt
x=np.arange(0.05,3,0.05)
y1=[math.log(a,1.5)for a in x]
y2=[math.log(a,2)for a in x]
y3=[math.log(a,3)for a in x]
plot1=plt.plot(x,y1,'-g',label="log1.5(x)")
plot2=plt.plot(x,y2,'-r',label="log2(x)")
plot3=plt.plot(x,y3,'-b',label="log3(x)")
plt.legend(loc='lower right')
plt.show()