Multidimensional lists in Python (original) (raw)

Multi-dimensional lists in Python

Last Updated : 09 Dec, 2018

There can be more than one additional dimension to lists in Python. Keeping in mind that a list can hold other lists, that basic principle can be applied over and over. Multi-dimensional lists are the lists within lists. Usually, a dictionary will be the better choice rather than a multi-dimensional list in Python.

Accessing a multidimensional list:

Approach 1:

a = [[ 2 , 4 , 6 , 8 , 10 ], [ 3 , 6 , 9 , 12 , 15 ], [ 4 , 8 , 12 , 16 , 20 ]]

print (a)

Output:

[[2, 4, 6, 8, 10], [3, 6, 9, 12, 15], [4, 8, 12, 16, 20]]

Approach 2: Accessing with the help of loop.

a = [[ 2 , 4 , 6 , 8 , 10 ], [ 3 , 6 , 9 , 12 , 15 ], [ 4 , 8 , 12 , 16 , 20 ]]

for record in a:

`` print (record)

Output:

[2, 4, 6, 8, 10] [3, 6, 9, 12, 15] [4, 8, 12, 16, 20]

Approach 3: Accessing using square brackets.
Example:

a = [ [ 2 , 4 , 6 , 8 ],

`` [ 1 , 3 , 5 , 7 ],

`` [ 8 , 6 , 4 , 2 ],

`` [ 7 , 5 , 3 , 1 ] ]

for i in range ( len (a)) :

`` for j in range ( len (a[i])) :

`` print (a[i][j], end = " " )

`` print ()

Output:

2 4 6 8 1 3 5 7 8 6 4 2 7 5 3 1

Creating a multidimensional list with all zeros:

m = 4

n = 5

a = [[ 0 for x in range (n)] for x in range (m)]

print (a)

Output:

[[0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0]]

Methods on Multidimensional lists

1. append(): Adds an element at the end of the list.
Example:

a = [[ 2 , 4 , 6 , 8 , 10 ], [ 3 , 6 , 9 , 12 , 15 ], [ 4 , 8 , 12 , 16 , 20 ]]

a.append([ 5 , 10 , 15 , 20 , 25 ])

print (a)

Output:

[[2, 4, 6, 8, 10], [3, 6, 9, 12, 15], [4, 8, 12, 16, 20], [5, 10, 15, 20, 25]]

2. extend(): Add the elements of a list (or any iterable), to the end of the current list.

a = [[ 2 , 4 , 6 , 8 , 10 ], [ 3 , 6 , 9 , 12 , 15 ], [ 4 , 8 , 12 , 16 , 20 ]]

a[ 0 ].extend([ 12 , 14 , 16 , 18 ])

print (a)

Output:

[[2, 4, 6, 8, 10, 12, 14, 16, 18], [3, 6, 9, 12, 15], [4, 8, 12, 16, 20]]

3. reverse(): Reverses the order of the list.

a = [[ 2 , 4 , 6 , 8 , 10 ], [ 3 , 6 , 9 , 12 , 15 ], [ 4 , 8 , 12 , 16 , 20 ]]

a[ 2 ].reverse()

print (a)

Output:

[[2, 4, 6, 8, 10], [3, 6, 9, 12, 15], [20, 16, 12, 8, 4]]