Multi-dimensional lists in Python

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:

# Python program to demonstrate printing
# of complete multidimensional list
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.

# Python program to demonstrate printing
# of complete multidimensional list row
# by row.
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:

# Python program to demonstrate that we
# can access multidimensional list using
# square brackets
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:

# Python program to create a m x n matrix
# with all 0s
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:

# Adding a sublist

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.

# Extending a sublist

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.

# Reversing a sublist

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]]