import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
a=np.arange(9).reshape(3,3)
print(a)
f  = a.ravel()
print(f)
# b = a[:,0]
# c = a[:,1]
# print(b)
# print(c)
# d  = np.dot(b, c.T)
# print(d)
# e  = np.dot(c, b.T)
# print(e)

