Nested List or Matrix

Nested List or Matrix using List

 A list in inside another list is called nested or a matrix. For example

>>>Student =[101, ‘Narain Ji’ ,[76,98,56,76,89]] # nested list

 

>>> Marks=[[87,'Jyotsna'],[98,'Ankita'],[77,'Vanshika']]

 

Index from left	0	1	2
	[0][0]   [0][1]	[1][0]  [1][1]	[2][1]  [2][2]
List of elements	[87,'Jyotsna']	[98,'Ankita']	[77,'Vanshika']
Index from right end	[-3][-2] [-3][-1]	[-2][-2] [-2][-1]	[-1][-2] [-1][-1]
	[-3][0]  [-3][1]	[-2][0] [-2][1]	[-1][0] [-1][1]
	-3	-2	-1

 

 

Creating Matrix

A matrix is a rectangular table of elements or two dimensional array. The following is a 3x3 matrix, meaning there are 3 rows and 3 columns.

 

If we know the number of rows(n) and columns(m) of a matrix, then the syntax is :

Matrix=[[0 for col in range(m)],for row in range(m)]

 Processing of Matrix :

Source Code

row_num = int(input("Input number of rows: "))

col_num = int(input("Input number of columns: "))

multi_list = [[0 for col in range(col_num)] for row in range(row_num)] # Create matrix

for row in range(row_num):

Display matrix

    for col in range(col_num):

        multi_list[row][col]= row*col

        print(multi_list[row][col],end="\t")

    print()

 

 Input Matrix/nested list elements from keyboard and show matrix

Source Code:

rows = int(input("Input number of rows: "))

cols = int(input("Input number of columns: "))

Matrix = [[0 for col in range(cols)] for row in range(rows)] # declare matrix

for row in range(rows):

    print("Enter values for row -> ",row)

    for col in range(cols):

        print("Matrix[",row,"][",col,"]-> ",end="")

        Matrix[row][col]=int(input()) # input elements from keyboard

print("\n Display Matrix ")

for row in range(rows):

    for col in range(cols):

        print(Matrix[row][col],end="\t")

    print()