Python – Numpy Array Column Deletion

Given a numpy array, write a programme to delete columns from numpy array. Examples –

Input: [['akshat', 'nikhil'], ['manjeeet', 'akash']]
Output:  [['akshat']['manjeeet']]

Input:  [[1, 0, 0, 1, 0], [0, 1, 2, 1, 1]]
Output:  [[1 0 1 0][0 2 1 1]]

  Given below are various methods to delete columns from numpy array. Method #1: Using np.delete()

Python3

# Python code to demonstrate
# deletion of columns from numpy array

import numpy as np

# initialising numpy array
ini_array = np.array([[1, 0, 0, 1, 0],
                        [0, 1, 2, 1, 1]])


# deleting second column from array
result = np.delete(ini_array, 1, 1)

# print result
print ("Resultant Array :"+str(result))

Output:

Resultant Array :[[1 0 1 0]
 [0 2 1 1]]

Time Complexity: O(n)

Space Complexity: O(n)

where n is length of array

Method #2: Using compress() and logical_not()

Python3

# Python code to demonstrate
# deletion of columns from numpy array

import numpy as np

# initialising numpy array
ini_array = np.array([[1, 0, 0, 1, 0], [1, 2, 0, 0, 1]])
z = [False, True, False, False, False]


# deleting second column from array
result = ini_array.compress(np.logical_not(z), axis = 1)

# print result
print ("Resultant Array :"+str(result))

Output:

Resultant Array :[[1 0 1 0]
 [1 0 0 1]]

Time Complexity: O(n)

Space Complexity: O(n)

where n is length of array

Method #3: Using logical_not()

Python3

# Python code to demonstrate
# deletion of columns from numpy array

import numpy as np

# initialising numpy array
ini_array = np.array([[1, 0, 0, 1, 0], [1, 2, 0, 0, 1]])
z = [False, True, False, False, False]


# deleting second column from array
result = ini_array[:, np.logical_not(z)]

# print result
print ("Resultant Array :"+str(result))

Output:

Resultant Array :[[1 0 1 0]
 [1 0 0 1]]

Time Complexity: O(n)

Space Complexity: O(n)

where n is length of array