# Python | Ways to add rows / columns in a NumPy array

Method # 1: Using `np.hstack()`

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``` # Python code for demo # add columns to the numpy array   import numpy as np    ini_array = np.array ([[ 1 , 2 , 3 ], [ 45 , 4 , 7 ], [ 9 , 6 , 10 ]])   # print the original array print ( "initial_array:" , str (ini_array));    # Array to be added as a column column_to_be_added = np.array ([ 1 , 2 , 3 ])   # Add a column to the numpy array result = np.hstack ((ini_array, np.atleast_2d (column_to_be_added) .T))    # print result print ( "resultant array" , str (result)) ```

Exit :

` initial_array: [[1 2 3] [45 4 7] [9 6 10]] resultant array [[1 2 3 1] [45 4 7 2] [9 6 10 3]] `

Method # 2: Using the ` column_stack () ` method

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``` # Python code to demonstrate # add columns to the numpy array   import numpy as np   ini_array = np. array ([[ 1 , 2 , 3 ], [ 45 , 4 , 7 ], [ 9 , 6 , 10 ]])   # print the original array print ( "initial_array:" , str (ini_array));    # Array to be added as a column column_to_be_added = np.array ([ 1 , 2 , 3 ])   # Add a column to the numpy array result = np.column_stack ((ini_array, column_to_be_added))   # print result print ( "resultant array" , str (re sult)) ```

Output:

``` initial_array: [[1 2 3] [45 4 7] [9 6 10]] resultant array [[1 2 3 1] [45 4 7 2] [9 6 10 3]]    Method # 3: Using `np.vstack()`      ` # Python code for demonstration `  ` # adding lines to the numy array `      ` import ` ` numpy as np `     ` ini_array ` ` = ` ` np.array ([[ ` ` 1 ` `, ` ` 2 ` `, ` ` 3 ` `], [` ` 45 ` `, < / code>  4  ,   7   ], [  9  ,   6  ,   10  ]]) ``     # print the original array     print   (  "initial_array:"  ,   str   (ini_array));      # Array to be added as a string     row_to_be_added   =   np.array ([  1  ,   2  ,   3  ])      # Add line to numpy array     result   =   np.vstack ((ini_array, row_to_be_added))      # print result     print   (  "resultant array"  ,   str   (result))   `         Exit:   initial_array: [[1 2 3] [45 4 7] [9 6 10]] resultant array [[1 2 3] [45 4 7] [9 6 10] [1 2 3]]

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