Python: Array vs List | Main Differences & When to use?

Python: Array vs List | Main Differences & When to use?

As a software developer, while you are developing a website, application, or any other software, some of you use arrays and some of you also use lists in your programs or codes. Am I right? But, have you ever thought of any differences between them? Did you compare them anytime? No, I guess.

You might not have compared them anytime maybe due to various reasons. But, comparing both arrays and lists will help you in many ways while you are developing a software, website, or any kind of application. Comparing helps you know which will be easier to use, which is more accurate, which will execute fast, and so on.

So, in this article, I am going to compare arrays and lists to know their uses and differences between them. In the end, you are going to know about the uses of arrays and lists in a program. You will come to know where to use an array and where to use a list. So, without making it late, let us go further.

First, let us know about an ‘Array’ in the Python programming language.

Arrays in Python

In general, it is a collection of similar data elements that we will store at various memory locations. It is the simplest form of data structure. Here, you can access each data element directly only by using the index number of an array. Arrays are also called as Sequences.

You will use Arrays when you want to work with many values of the same Python data type. For this, you can consider examples such as student names, employee numbers, etc. Using arrays, you will be able to store related pieces of data that belong. With the help of arrays, it will be easy to perform the same operation on multiple values at the same time.

Let us see a few examples to understand an array program in Python. Consider the following examples:

Example-1:

import array

int_array = array.array(‘i’, [1, 2, 3, 4])

for m in int_array:

    print(m)

for n in range(0, len(int_array)):

    print(f’int_array[{n}] = {int_array[n]}’)

After running the above program, you will get the following output:

Output:

int_array[0] = 1

int_array[1] = 2

int_array[2] = 3

int_array[3] = 4

Now, let us see another example:

Example-2:

def sum1(arr):

    res = 0

    for x in arr:

        res += x

    return res

def sum_2(arr):

    res = sum(arr)

    return res

if __name__ == “__main__”:

    arr = [1, 2, 3, 4, 5]

    print (‘sum1: {}’.format(sum1(arr)))

    print (‘sum2: {}’.format(sum2(arr)))

After running the above program, you will get the following output:

Sum1: 15

Sum2: 15

Uses of Arrays in Python:

  1. You can use Python arrays when you need to use many same-type variables in your program.
  2. Using arrays, you can also store the data collected by you while creating software.
  3. You will use the arrays especially when you have to process the data dynamically.
  4. As Python uses less memory, arrays are much faster than lists.
  5. You can also use arrays to implement many other data structures, such as lists and strings.
  6. Using arrays, you can exploit the addressing logic of computers effectively.
  7. While programming in python, it is better to use an array when you have a very long sequence of items. You will get more efficient data storage in arrays.
  8. You can use this also when you plan to do any numerical operations with your combination of items.  
  9. These days, Data analytics and data science are depending heavily on arrays. Numpy is an example of this.

Advantages of Array

  1. Arrays can be used to optimize the code easily. When you write a small piece of code, you can store a large number of values in a single array. So, you don’t need to declare each variable separately.
  2. You can use arrays easily because they consist of many algorithms like searching and sorting techniques. You can find maximum and minimum values, and you can also implement reversing using arrays.
  3. The time complexity to access any element of an array is O(1), i.e, it takes a constant amount of time to access an element.
  4. You can easily identify elements of Arrays because they use indexes to identify their elements.
  5. We can also store elements of a matrix of any dimensions because there are 2-dimensional arrays also along with simple arrays.
  6. You don’t need to allocate extra memory outside the contiguous block because arrays store elements in contiguous locations. It helps you to prevent wastage of memory.
  7. You can use arrays also to implement other data structures like linked lists, stacks, queues, graphs, trees, etc.
  8. Arrays can be used to implement many CPU Scheduling techniques.

Disadvantages of Array

  1. The fixed size of an array is one of the biggest disadvantages of an array.
  2. Once you allocate the memory to an array, you cannot increase or decrease the memory. So, even if you want to store extra data in an array, you can do it.
  3. Less memory is allocated than required which leads to loss of data.
  4. As an array is homogenous in nature, you cannot store values of different data types in a single array.
  5. As they store data in contiguous memory locations, you cannot perform deletion and insertion operations. But you can implement linked lists which provide random access to elements to overcome this problem.

Lists in Python

In Python, a data structure that you will use to store the sequence of various types of data is known as a ‘List’. Unlike arrays, you can modify the elements in Python lists because they are the mutable type which means the element can be modified even after it is created. However, there are six data types in python that can store the sequences, but a list is the most common and reliable type among all of them.

In another way, you can define a list as a collection of values or items of different types. You will observe items in the list are separated with the comma (,) and enclosed with the square brackets [].

Let us see a simple example of a list. Consider the following example:

Example-1:

a = [1, 2, 3, 5]

b = [1, 2]

l1 = []

for i in a:

    if i not in b:

        l1.append(i)

The following will be the output of the above program:

Output: [3,5]

Uses of Lists in Python

  1. Lists are used to store multiple items in a single variable
  2. Lists are great to use when you want to work with many related values.
  3. They enable you to keep data together that belongs together, condense your code, and perform the same methods and operations on multiple values at once
  4. List Comprehensions that are easy to understand and make code elegant. We can write the program with simple expressions.
  5. List comprehensions are way faster than for loop and other methods like a map.
  6. List is the most important Python built-in container, being a key aspect when programming in Python to understand them properly.
  7. A list may be used for a variety of purposes, such as storing objects or removing and adding objects.

Differences Between A List And An Array

You can find only a few differences between a list and an array because they are almost similar. So, let us observe some of the differences between them.

  1. In python, a List is used to collect items that usually consist of elements of multiple data types whereas an array collects several items of the same data type.
  2. You cannot manage arithmetic operations using a list whereas using Array, you can manage all arithmetic operations.
  3. There are elements that belong to the different data types in a list but an array consists of elements that belong to the same data type only.
  4. The list is flexible in nature because the list is perfect as it allows easy modification of data whereas the array is not suitable as it does not allow easy modification of data. Thus, it is not flexible in nature.
  5. Larger memory is consumed by a list whereas an array consumes less memory when compared to a list.
  6. To access a list, you don’t need any specific looping. But to access the components of the array, a loop is mandatory.
  7. A shorter sequence of data is favored by a list whereas a longer sequence of data is favored by an array.
  8. It is possible to print the entire list without the help of an explicit loop but to print or access array elements, you should have an explicit loop.

Hence I conclude that you don’t need any module or package to be imported before using in a list in python because it is the in-build data structure of python language. But in the case of an array, you have to import the “array” module before creating, and using arrays because it is not an in-build data structure for python language.

This is all about a list and an array in the Python programming language. Therefore, in this article, you have come to know about when to use arrays and lists in python while you are programming. You also came to know the major differences between them. Thank you for reading the article. I hope this article will help you for sure.

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