Python 2D array

An array is a collection of linear data structures that contain all elements of the same data type in contiguous memory space. It is like a container that holds a certain number of elements that have the same data type. An array's index starts at 0, and therefore, the programmer can easily obtain the position of each element and perform various operations on the array. In this section, we will learn about 2D (two dimensional) arrays in Python.

Two-Dimensional Array (2D Array)

A 2D array is an array of arrays that can be represented in matrix form like rows and columns. In this array, the position of data elements is defined with two indices instead of a single index.

Syntax

Array_name = [rows][columns] # declaration of 2D array
Arr-name = [ [m1, m2, m3, … . m_n], [n1, n2, n3, … .. n_n] ]

Where m is the row and n is the column of the table.

Access Two-Dimensional Array

In Python, we can access elements of a two-dimensional array using two indices. The first index refers to the indexing of the list and the second index refers to the position of the elements. If we define only one index with an array name, it returns all the elements of 2-dimensional stored in the array.

Let's create a simple program to understand 2D (two dimensional) arrays in Python.

2dSimple.py

Student_dt = [ [72, 85, 87, 90, 69], [80, 87, 65, 89, 85], [96, 91, 70, 78, 97], [90, 93, 91, 90, 94], [57, 89, 82, 69, 60] ]
#print(student_dt[])
print(Student_dt[1]) # print all elements of index 1
print(Student_dt[0]) # print all elements of index 0
print(Student_dt[2]) # print all elements of index 2
print(Student_dt[3][4]) # it defines the 3rd index and 4 position of the data element.

Output:

In the above example, we passed 1, 0, and 2 as parameters into 2D array that prints the entire row of the defined index. And we have also passed student_dt[3][4] that represents the 3^rd index and 4^th position of a 2-dimensional array of elements to print a particular element.

Traversing the element in 2D (two dimensional)

Program.py

# write a program to traverse every element of the two-dimensional array in Python.
Student_dt = [ [72, 85, 87, 90, 69], [80, 87, 65, 89, 85], [96, 91, 70, 78, 97], [90, 93, 91, 90, 94], [57, 89, 82, 69, 60] ]
# Use for loop to print the entire elements of the two dimensional array.
for x in Student_dt:  # outer loop
    for i in x:  # inner loop
        print(i, end = " ") # print the elements
    print()

Output:

Insert elements in a 2D (Two Dimensional) Array

We can insert elements into a 2 D array using the insert() function that specifies the element' index number and location to be inserted.

Insert.py

# Write a program to insert the element into the 2D (two dimensional) array of Python.
from array import * # import all package related to the array.
arr1 = [[1, 2, 3, 4], [8, 9, 10, 12]]  # initialize the array elements.
print("Before inserting the array elements: ")
print(arr1) # print the arr1 elements.
# Use the insert() function to insert the element that contains two parameters.
arr1.insert(1, [5, 6, 7, 8])  # first parameter defines the index no., and second parameter defines the elements
print("After inserting the array elements ")
for i in arr1: # Outer loop
    for j in i: # inner loop
        print(j, end = " ") # print inserted elements.
    print()    

Output:

Update elements in a 2 -D (Two Dimensional) Array

In a 2D array, the existing value of the array can be updated with a new value. In this method, we can change the particular value as well as the entire index of the array. Let's understand with an example of a 2D array, as shown below.

Create a program to update the existing value of a 2D array in Python.

Update.py

from array import * # import all package related to the array.
arr1 = [[1, 2, 3, 4], [8, 9, 10, 12]]  # initialize the array elements.
print("Before inserting the array elements: ")
print(arr1) # print the arr1 elements.


arr1[0] = [2, 2, 3, 3] # update the value of the index 0
arr1[1][2] = 99 # define the index [1] and position [2] of the array element to update the value.
print("After inserting the array elements ")
for i in arr1: # Outer loop
    for j in i: # inner loop
        print(j, end = " ") # print inserted elements.
    print() 

Output:

Delete values from a 2D (two Dimensional) array in Python

In a 2- D array, we can remove the particular element or entire index of the array using del() function in Python. Let's understand an example to delete an element.

Delete.py

from array import * # import all package related to the array.
arr1 = [[1, 2, 3, 4], [8, 9, 10, 12]]  # initialize the array elements.
print("Before Deleting the array elements: ")
print(arr1) # print the arr1 elements.

del(arr1[0][2]) # delete the particular element of the array.
del(arr1[1]) # delete the index 1 of the 2-D array.

print("After Deleting the array elements ")
for i in arr1: # Outer loop
    for j in i: # inner loop
        print(j, end = " ") # print inserted elements.
    print()    

Output:

Size of a 2D array

A len() function is used to get the length of a two-dimensional array. In other words, we can say that a len() function determines the total index available in 2-dimensional arrays.

Let's understand the len() function to get the size of a 2-dimensional array in Python.

Size.py

array_size = [[1, 3, 2],[2,5,7,9], [2,4,5,6]] # It has 3 index
print("The size of two dimensional array is : ")
print(len(array_size)) # it returns 3 

array_def = [[1, 3, 2], [2, 4, 5, 6]] # It has 2 index
print("The size of two dimensional array is : ")
print(len(array_def)) # it returns 2

Output:

Write a program to print the sum of the 2-dimensional arrays in Python.

Matrix.py

def two_d_matrix(m, n): # define the function
    Outp = []  # initially output matrix is empty
    for i in range(m): # iterate to the end of rows
        row = []
        for j in range(n): # j iterate to the end of column
            num = int(input(f "Enter the matrix [{0}][{j}]"))
            row.append(num) # add the user element to the end of the row
        Outp.append(row) # append the row to the output matrix
    return Outp    

def sum(A, B): # define sum() function to add the matrix.
    output = [] # initially, it is empty.
    print("Sum of the matrix is :")
    for i in range(len(A)): # no. of rows
        row = []
        for j in range(len(A[0])): # no. of columns
            
            row.append(A[i][j] + B[i][j]) # add matrix A and B
        output.append(row)
    return output    # return the sum of both matrix

m = int(input("Enter the value of m or Row\n")) # take the rows
n = int(input("Enter the value of n or columns\n")) # take the columns

print("Enter the First matrix ") # print the first matrix
A = two_d_matrix(m, n) # call the matrix function
print("display the first (A) matrix")
print(A) # print the matrix

print("Enter the Second (B) matrix ")
B = two_d_matrix(m, n) # call the matrix function
print("display the Second (B) matrix")
print(B) # print the B matrix

s= sum(A, B) # call the sum function
print(s) # print the sum of A and B matrix.

Output: