Python | Ways to add row/columns in numpy array

Given numpy array, the task is to add rows/columns basis on requirements to numpy array. Let’s see a few examples of this problem.

Method #1: Using np.hstack() method

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# Python code to demonstrate
# adding columns in numpy array
  
import numpy as np
  
ini_array = np.array([[1, 2, 3], [45, 4, 7], [9, 6, 10]])
  
# printing initial array
print("initial_array : ", str(ini_array));
  
# Array to be added as column
column_to_be_added = np.array([1, 2, 3])
  
# Adding column to numpy array
result = np.hstack((ini_array, np.atleast_2d(column_to_be_added).T))
  
# printing result
print ("resultant array", str(result))

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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 #2: Using column_stack() method

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# python code to demonstrate
# adding columns in numpy array
  
import numpy as np
  
ini_array = np.array([[1, 2, 3], [45, 4, 7], [9, 6, 10]])
  
# printing initial array
print("initial_array : ", str(ini_array));
  
# Array to be added as column
column_to_be_added = np.array([1, 2, 3])
  
# Adding column to numpy array
result = np.column_stack((ini_array, column_to_be_added))
  
# printing result
print ("resultant array", str(result))

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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() method

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# python code to demonstrate
# adding rows in numpy array
  
import numpy as np
  
ini_array = np.array([[1, 2, 3], [45, 4, 7], [9, 6, 10]])
  
# printing initial array
print("initial_array : ", str(ini_array));
  
# Array to be added as row
row_to_be_added = np.array([1, 2, 3])
  
# Adding row to numpy array
result = np.vstack ((ini_array, row_to_be_added) )
  
# printing result
print ("resultant array", str(result))

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Output:

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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