import numpy as np

# [[ 1  2  3  4]
#  [ 5  6  7  8]
#  [ 9 10 11 12]]
a = np.array([[1,2,3,4], 
              [5,6,7,8], 
			  [9,10,11,12]])

# [[2 3]
#  [6 7]]
b = a[:2, 1:3]

print a[0, 1]
b[0, 0] = 77  
print a[0, 1] 