Mastering Loops in Python

Loops are essential in programming because they allow you to execute a block of code multiple times. Python offers two main types of loops—for and while—each serving different needs. In this blog, you’ll learn about loops, how to use them effectively, and explore some practical examples that demonstrate their power.

Why Use Loops?

• Loops help automate repetitive tasks.
• They improve code efficiency by minimizing repetition.
• Common scenarios include iterating over lists, repeating actions based on conditions, and processing items in collections.

The for Loop

The for loop in Python is typically used to iterate over a sequence (like a list, tuple, string, or range). The loop runs for each item in the sequence.

Syntax:

for item in sequence:
    # Code block to execute for each item

Example: Printing Each Item in a List

fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
    print(fruit)

Exercise: Iterate Through a List

Create a list of five favorite animals. Use a for loop to print each animal’s name.

Expected Output :

Lion
Tiger
Elephant
Dolphin
Panda

Output

 A Journey Through Time, DEC-2023Read more

Run

The range() Function

The range() function generates a sequence of numbers, making it useful for creating numeric loops.

Syntax:

for i in range(start, stop, step):
    # Code block

Example: Using range to Print Numbers from 1 to 5

for i in range(1, 6):
    print(i)

Exercise: Print Even Numbers

Write a for loop that uses range() to print even numbers between 2 and 10.

Expected Output :

2
4
6
8
10

Output

STEMRead more

Run

The while Loop

The while loop executes as long as a given condition is True. It’s especially useful when the number of iterations isn’t predetermined.

Syntax:

while condition:
    # Code block

Example: Counting Down from 5

count = 5
while count > 0:
    print(count)
    count -= 1

Exercise: Simple Countdown

Write a while loop that starts at 10 and counts down to 1. Print each number.

Expected Output :

10
9
8
7
6
5
4
3
2
1

Controlling Loops with break and continue

• break: Exits the loop when encountered.
• continue: Skips the current iteration and moves to the next one.

Example: Using break to Stop at a Specific Condition

for i in range(1, 6):
    if i == 3:
        break
    print(i)  # Stops printing when i == 3

Example: Using continue to Skip a Condition

for i in range(1, 6):
    if i == 3:
        continue
    print(i)  # Skips printing when i == 3

Exercise: Skip Odd Numbers

Write a for loop from 1 to 10. Use continue to skip printing any odd numbers.

2
4
6
8
10

Looping Through Strings

Strings are iterable in Python, meaning you can use loops to access each character individually.

Example: Print Each Character in a Word

word = "Python"
for letter in word:
    print(letter)

Exercise: Count Vowels

Write a loop that counts and prints the number of vowels in the word “education“.

Expected Output :

Number of vowels: 5

Conclusion

Loops are fundamental for efficient programming, enabling you to handle repetitive tasks with ease. By mastering loops, you can process data, automate tasks, and write cleaner, more efficient code. With practice, you’ll find endless possibilities for applying loops in your projects!