aarti_code.py

import numpy as np

A = np.array([[ 1,  0,  1,  0],
       [-1,  1,  0,  1],
       [ 0, -1,  0, -1],
       [ 0,  0, -1,  0],
       [ 0,  0,  0,  0]])

def cluster_columns(M):
    column_dict = {}
    for i in range(M.shape[1]):
        t = tuple(M[:,i])
        if t in column_dict:
            column_dict[t] += 1
        else:
            column_dict[t] = 1
    return column_dict

print(cluster_columns(A))
A_dropped_0 = np.array(list(cluster_columns(A).keys())).T
print(A_dropped_0)
print("Alternatively:")
A_dropped = np.array([i for i in set([tuple(A[:,i]) for i in range(A.shape[1])])]).T
print(A_dropped)