Numpy inverts a non-invertible matrix

Question

My friend and I executed this lines of code in Python 2 and Python 3:

import numpy as np  
mat = np.array([[1,0,0],[-1,3,3],[1,2,2]         


        

Answer 1

Rank=2 means the matrix is not invertible. For a 3x3 matrix to be invertible, its rank must be 3.