How do I create a multidimensional list in Python?

Multidimensional lists are lists within lists that allow you to store data in a table-like structure. You access elements using two indices: the first for the row and the second for the column, like list[row][column].

Basic Structure

In a multidimensional list, each element can be accessed using bracket notation ?

list[r][c]

Where r is the row number and c is the column number. For example, a 2x3 multidimensional list would be accessed as list[2][3].

Creating a Multidimensional List

You can create a multidimensional list by nesting lists inside another list ?

# Create a Multi-Dimensional Python List
mylist = [[2, 5], [10, 24, 68], [80]]

print("Multidimensional List")
for row in mylist:
    print(row)

Multidimensional List
[2, 5]
[10, 24, 68]
[80]

Accessing Elements

Access specific elements using square brackets with two indices ?

# Create a Multi-Dimensional Python List
mylist = [[2, 5], [10, 24, 68], [80]]

print("Multidimensional List")
for row in mylist:
    print(row)

# Accessing third element in the 2nd row (index 1, element 2)
print("\nThird element in the 2nd row =", mylist[1][2])

# Accessing first element in the 1st row
print("First element in the 1st row =", mylist[0][0])

Multidimensional List
[2, 5]
[10, 24, 68]
[80]

Third element in the 2nd row = 68
First element in the 1st row = 2

Adding Elements

Use the append() method to add new rows to a multidimensional list ?

# Create a Multi-Dimensional Python List
mylist = [[2, 5], [10, 24, 68], [80]]

print("Original Multidimensional List")
for row in mylist:
    print(row)

# Append a new row
mylist.append([65, 24])

print("\nAfter appending [65, 24]:")
for row in mylist:
    print(row)

# Append elements to an existing row
mylist[0].append(99)

print("\nAfter appending 99 to first row:")
for row in mylist:
    print(row)

Original Multidimensional List
[2, 5]
[10, 24, 68]
[80]

After appending [65, 24]:
[2, 5]
[10, 24, 68]
[80]
[65, 24]

After appending 99 to first row:
[2, 5, 99]
[10, 24, 68]
[80]
[65, 24]

Creating Regular Multidimensional Lists

For matrices with equal rows and columns, you can use list comprehension ?

# Create a 3x3 matrix filled with zeros
rows, cols = 3, 3
matrix = [[0 for j in range(cols)] for i in range(rows)]

print("3x3 Matrix:")
for row in matrix:
    print(row)

# Fill with some values
matrix[0][0] = 1
matrix[1][1] = 5
matrix[2][2] = 9

print("\nAfter adding values:")
for row in matrix:
    print(row)

3x3 Matrix:
[0, 0, 0]
[0, 0, 0]
[0, 0, 0]

After adding values:
[1, 0, 0]
[0, 5, 0]
[0, 0, 9]

Conclusion

Multidimensional lists are created by nesting lists within lists. Use list[row][col] to access elements and append() to add new rows. For regular matrices, list comprehension provides an efficient creation method.