How To Iterate Through A 2D Array In Python?

As a Python developer during a project for one of my USA clients, I had a requirement to iterate through a 2D array in Python. I discovered many ways to achieve this task. We will go through detailed examples to learn how to iterate through a 2D array in Python.

Table of Contents

What are 2D Arrays in Python?

2D array in Python is a list of lists. Each element in the outer list represents a row, and each element within a row represents a column. Here’s an example of a 2D array:

students = [
    ['John', 'New York', 85],
    ['Emily', 'California', 92],
    ['Michael', 'Texas', 78],
    ['Jessica', 'Florida', 89]
]

In this example, we have a 2D array students that stores information about students, including their names, states, and grades.

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Access Specific Elements from Python Array

Sometimes, you may need to access specific elements in a 2D array. You can do this by using the row and column indices. Here’s an example:

print(students[1][0]) 
print(students[2][2])

Output:

Emily
 78

A screenshot of the executed example code is added below, you can have a look.

How to Iterate Through a 2D Array in Python

In this example, students[1][0] accesses the element at the second row and first column, “Emily”. Similarly, students[2][2] access the element of the third row and third column, “78”.

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Method 1. Iterating Through a 2D Array

Iterate through a 2D array in Python, using nested loops. The outer loop iterates over the rows, while the inner loop iterates over the columns within each row. Here’s an example:

for row in students:
    for item in row:
        print(item, end=' ')
    print()

Output:

John New York 85 
Emily California 92 
Michael Texas 78 
Jessica Florida 89

A screenshot of the executed example code is added below, you can have a look.

In this example, the outer loop for row in students iterates over each row of the students array. The inner loop for item in row iterates over each item within a row. We print each item followed by a space, and after each row, we use print() it to move to the next line.

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Method 2. Using enumerate() for Iteration

Python provides the enumerate() function, that allows you to iterate over a sequence and retrieve the index and the value at each iteration. You can use enumerate() to iterate through a 2D array and access the row index and row elements. Here’s an example:

for row_index, row in enumerate(students):
    print(f"Row {row_index + 1}:")
    for item in row:
        print(item, end=' ')
    print()

Output:

Row 1:
John New York 85
Row 2: 
Emily California 92
Row 3:
Michael Texas 78 
Row 4:
Jessica Florida 89

A screenshot of the executed example code is added below, you can have a look.

Iterate Through a 2D Array in Python Using enumerate() for Iteration

In this example, enumerate(students) returns a tuple for each row, where the first element is the row index, and the second element is the row itself. We use row_index to print the row number, and then iterate over each item in the row using the inner loop.

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Method 3. Iterate Through Columns

If you need to iterate through the columns of a 2D array, you can use the zip() function along with the unpacking operator *. Here’s an example:

for column in zip(*students):
    print(column)

Output:

('John', 'Emily', 'Michael', 'Jessica')
('New York', 'California', 'Texas', 'Florida')
(85, 92, 78, 89)

In this example, zip(*students) unpack the students array into separate arguments, which are then passed to the zip() function. The zip() function combines the corresponding elements from each row into tuples. We then iterate over each column using the for loop.

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Modify Elements in a Python 2D Array

You can modify elements in a 2D array by accessing them using the row and column indices and assigning new values. Here’s an example:

students[2][2] = 80
print(students)

Output:

[['John', 'New York', 85], ['Emily', 'California', 92], ['Michael', 'Texas', 80], ['Jessica', 'Florida', 89]]

In this example, we modify the element at the third row and third column by assigning it a new value of 80. The updated 2D array is then printed.

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Conclusion

In this tutorial, I have explained how to iterate through a 2D array in Python, I explained what are 2D arrays in Python, And how to access specific elements from Python Array. I discussed how to Iterate through a 2D array using nested loops, And also functions like enumerate() and zip() that can be helpful in certain conditions. I showed how to modify elements in a Python 2D array.

I hope this tutorial has helped you understand how to iterate through a 2D array in Python. Happy coding!