import random

l = [random.expovariate(2) for k in range(200)]
sum(l) / float(len(l))

l = [random.expovariate(1) for k in range(200)]
sum(l) / float(len(l))

l = [random.expovariate(.5) for k in range(200)]
sum(l) / float(len(l))

import matplotlib.pyplot as plt
%matplotlib inline

plt.scatter([1,2,3,4], [4,5,6,7]);