NumPy: Add a new row to an empty numpy array

Last update on August 29 2025 12:49:22 (UTC/GMT +8 hours)

Add Row to Empty Array

Write a NumPy program to add another row to an empty NumPy array.

Sample Solution:

Python Code:

# Importing the NumPy library and aliasing it as 'np'
import numpy as np

# Creating an empty NumPy array with shape (0, 3) of integers
arr = np.empty((0, 3), int)

# Printing a message indicating an empty array will be displayed
print("Empty array:")

# Displaying the empty array
print(arr)

# Appending two new arrays to the 'arr' array vertically along axis 0
arr = np.append(arr, np.array([[10, 20, 30]]), axis=0)
arr = np.append(arr, np.array([[40, 50, 60]]), axis=0)

# Printing a message indicating that two new arrays are added to the original array
print("After adding two new arrays:")

# Displaying the updated 'arr' array after adding two new arrays
print(arr) 

Sample Output:

Empty array:
[]
After adding two new arrays:
[[10 20 30]
 [40 50 60]]

Explanation:

In the above exercise -

• arr = np.empty((0,3), int): This line creates an empty NumPy array named ‘arr’ with shape (0, 3) and integer data type. The array has no rows and 3 columns.
• arr = np.append(arr, np.array([[10,20,30]]), axis=0): Append a new row [10, 20, 30] to the ‘arr’ array along axis 0 (row-wise). After this operation, the shape of ‘arr’ becomes (1, 3).
• arr = np.append(arr, np.array([[40,50,60]]), axis=0): Append another row [40, 50, 60] to the ‘arr’ array along axis 0 (row-wise). After this operation, the shape of ‘arr ‘ becomes (2, 3).
• Finally print(arr) function prints the array.

Pictorial Presentation:

For more Practice: Solve these Related Problems:

• Write a NumPy program to initialize an empty array and then append a new row using np.vstack.
• Create a function that checks if an array is empty and adds a row only if it meets certain conditions.
• Test the row addition on an empty array and verify that the shape is updated correctly.
• Implement a solution that dynamically adds multiple rows to an empty array and prints the result.

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