Python 2D Arrays

# Python 2D Arrays - Basics of Python - Software Development

 Table of contents What is a 2D Array? Creating a 2D Array Accessing Elements in a 2D Array Iterating Over a 2D Array Modifying Elements in a 2D Array Sample Problems ## What is a 2D Array?

In Python, a 2D array, also known as a two-dimensional array, is a data structure that represents a matrix or a table-like structure consisting of rows and columns. Unlike a 1D array, which is a linear sequence of elements, a 2D array allows you to organize and access data in a grid-like format.

Each element in a 2D array is identified by its row and column indices. Rows are numbered from top to bottom, and columns are numbered from left to right.

## Creating a 2D Array

In Python, you can create a 2D array using nested lists. Each element in the outer list represents a row, and each element within the row represents a column value.
Here's an example of creating a 2D array with three rows and three columns:

# Creating a 2D array

my_array = [[1, 2, 3],

[4, 5, 6],

[7, 8, 9]]

In the above example, 'my_array' is a 2D array with three rows and three columns. It can be visualized as follows:

1  2  3

4  5  6

7  8  9

## Accessing Elements in a 2D Array

To access a specific element in a 2D array, you can use the row and column indices.
For example, to access the element in the second row and third column of the 'my_array':

# Accessing an element in a 2D array

element = my_array

print(element)  # Output: 6

In the above code, 'my_array' returns the value '6', which is the element in the second row and third column.

## Iterating Over a 2D Array

You can use nested loops to iterate over all the elements in a 2D array.

# Iterating over a 2D array

for row in my_array:

for element in row:

print(element, end=' ')

print()

Output:

1 2 3

4 5 6

7 8 9

In the above code, the outer loop iterates over each row, and the inner loop iterates over each element within the row. By printing each element and adding a newline character after each row, we can display the entire 2D array.

## Modifying Elements in a 2D Array

You can modify elements in a 2D array by assigning a new value to a specific element using its row and column indices.

# Modifying an element in a 2D array

my_array = 10

print(my_array)

Output:

[[1, 2, 3],

[4, 5, 10],

[7, 8, 9]]

In the above code, 'my_array' is modified from '6' to '10'. The resulting array is:

1  2  3

4  5  10

7  8  9

## Sample Problems

Here are a few sample problems that you can solve using 2D arrays:

Problem 1: Finding the Sum of all Elements in a 2D Array
Given a 2D array, write a program to find the sum of all its elements.

# Problem 1: Finding the Sum of all Elements in a 2D Array

def find_sum_2d_array(arr):

total_sum = 0

for row in arr:

for element in row:

total_sum += element

# Test the function

my_array = [[1, 2, 3],

[4, 5, 6],

[7, 8, 9]]

print(find_sum_2d_array(my_array))  # Output: 45

Problem 2: Transposing a 2D Array

Given a 2D array, write a program to transpose it, i.e., convert its rows into columns and columns into rows.

# Problem 2: Transposing a 2D Array

def transpose_2d_array(arr):

transposed_array = []

for col_index in range(len(arr)):

transposed_row = []

for row in arr:

transposed_row.append(row[col_index])

transposed_array.append(transposed_row)

return transposed_array

# Test the function

my_array = [[1, 2, 3],

[4, 5, 6],

[7, 8, 9]]

transposed = transpose_2d_array(my_array)

for row in transposed:

print(row)

Output:

[1, 4, 7]

[2, 5, 8]

[3, 6, 9]

In the above code, the 'transpose_2d_array' function transposes the given array by swapping rows with columns.

### Conclusion

You've learned the basics of 2D arrays in Python. You now know how to create, access, iterate over, and modify elements in a 2D array. Additionally, you've solved a couple of sample problems to solidify your understanding.

The document Python 2D Arrays | Basics of Python - Software Development is a part of the Software Development Course Basics of Python.
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