Posted in numpy, Python

Python : Appending arrays in NumPy with practical examples

   November 16, 2023

In the world of data manipulation and scientific computing in Python, NumPy stands out for its efficiency and versatility. A fundamental operation in NumPy is appending arrays – a process essential for data aggregation, preprocessing, and transformation. This article provides a detailed guide on how to append arrays in NumPy, illustrated with practical examples. Appending arrays in NumPy is a straightforward yet powerful operation

Understanding array appending in NumPy

Appending arrays means adding elements from one array to the end of another. In NumPy, this is often done using the numpy.append() function, which offers flexibility in handling different array dimensions and shapes.

Creating sample arrays

Let’s create some sample arrays to demonstrate appending operations. We’ll use arrays representing names for a relatable context.

Example Arrays Creation
import numpy as np
# Sample arrays
array1 = np.array(['Sachin', 'Ram'])
array2 = np.array(['Raju', 'David', 'Wilson'])
print("Array 1:", array1)
print("Array 2:", array2)
Output
Array 1: ['Sachin' 'Ram']
Array 2: ['Raju' 'David' 'Wilson']

Appending arrays
Now, let’s append array2 to array1 using the numpy.append() function.

Using numpy.append()

# Appending array2 to array1
appended_array = np.append(array1, array2)
print("Appended Array:", appended_array)

This code appends the elements of array2 to array1, resulting in a single combined array.

Understanding the code

  • np.append(array1, array2): This function takes two arrays as inputs and returns a new array with the elements of the second array added to the end of the first array.

Use cases and considerations

  • Dimension Matching: The arrays must have compatible dimensions for appending. For higher-dimensional arrays, consider using np.concatenate or np.vstack / np.hstack for more control over the appending process.
  • In-Place Modification: Unlike lists in Python, appending to an array in NumPy does not modify the array in place. It creates a new array.
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