Python Program to remove the last given number of items from the array

An array is a data structure, which is used to store a set of elements of the same data type. And each element in the array is identified by key or index value.

Arrays in Python

In Python doesn’t have a native data structure to represent arrays. However, we can use Lists to represent arrays.

[1, 2, 3, 4, 5]

Also we can use array or NumPy modules to work with arrays in python.

An array defined by the array module is −

array('i', [1, 2, 3, 4])

A Numpy array defined by the NumPy module is −

array([1, 2, 3, 4])

Python indexing is starts from 0. And the above all arrays are indexed from starting 0 to (n-1).

Negative indexing

Python also supports negative indexing which is nothing but counting from the end of the array.

[1, 2, 3, 4, 5]
-5 -4 -3 -2 -1

The first element is identified by the index value –n and last element is -1. In most of the examples below we will use the negative indices to remove the last given number of items.

Input Output Scenarios

Assume we have an input array with 9 integer values. And in output the last few items will be removed based on the specified number.

Input array:
[1, 2, 3, 4, 5, 6, 7, 8, 9]
Output:
[1, 2, 3, 4, 5, 6]

The last 3 items 7, 8, 9 are removed from the input array.

Using List

By using python list.pop() method we can remove the last element of an array. Following is the syntax to do so –

list.pop(index)

The pop() method removes an item from a given index and returns the removed item, by default it removes the last element.

Example

In this example we will iterate the for loop up to the given number and then remove the last elements from the array.

# creating array
lst = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] 
print ("The original array is: ", lst) 
print() 

numOfItems = 4
# remove last elements
for i in range(numOfItems):
    lst.pop()
print ("The result is: ", lst) 

Output

The original array is:  [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
The result is:  [1, 2, 3, 4, 5, 6]

The last 4 elements 7, 8, 9, 10 are removed from the array.

Example

Let’s take an example and apply list slicing to remove the last element from an array.

# creating array
lst = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] 
print ("The original array is: ", lst) 
print() 

numOfItems = 4
# remove last elements
result = lst[:-numOfItems]
print ("The result is: ", result)

Output

The original array is:  [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
The result is:  [1, 2, 3, 4, 5, 6]

By using list negative indexing and slicing technique we have removed the last 4 items from the given array. Here the original array list does not affect which remains the same.

Using NumPy array

By using the numpy module and slicing technique we can easily remove the number of items from an array. Following is the syntax –

Numpy_array_obj[start:stop:step]

Example

Let’s take a NumPy array and remove the last 2 elements.

import numpy

# creating array
numpy_array = numpy.random.randint(1, 10, 5)
print ("The original array is: ", numpy_array) 
print() 

numOfItems = 2

# remove last elements
result = numpy_array[:-numOfItems]
print ("The result is: ", result) 

Output

The original array is:  [1 7 9 4 9]
The result is:  [6 6 3]

We have successfully removed the last 2 elements from the numpy array using the negative indexing.

Using the array module

The python array module also supports the array indexing, and slicing techniques to access the elements.

Example

In this example, we will create an array using the array module.

import array
# creating array
arr = array.array('i', [2, 4, 6, 8, 10])
print ("The original array is: ", arr) 
print() 
numOfItems = 2
# remove last elements
result = arr[:-numOfItems]
print ("The result is: ", result) 

Output

The original array is:  array('i', [2, 4, 6, 8, 10])
The result is:  array('i', [2, 4, 6])

The last 2 elements are removed from the array.