Not able to plot real time graph using matplotlib

I have written the following code with the help of online search. My intention here is to get a real time graph with time on x axis and some randomly generated value on y axis

import matplotlib.pyplot as plt
import matplotlib.animation as animation
import time
import numpy as np

fig = plt.figure()
ax1 = fig.add_subplot(1,1,1)

def animate(i):
    xar = []
    yar = []
    x,y = time.time(), np.random.rand()
    xar.append(x)
    yar.append(y)
    ax1.clear()
    ax1.plot(xar,yar)
ani = animation.FuncAnimation(fig, animate, interval=1000)
plt.show() 

With the above code I just see the range of y axis changing continuously and the graph will not appear in the figure.