Section 1.1: The Basics of the While Loop

The while loop in Python allows you to execute a block of code repeatedly, provided that a given condition is true. The syntax is straightforward:

while condition:

# execute this block of code

In this context, the condition is evaluated before each iteration. If it returns True, the code within the loop executes. This cycle continues until the condition evaluates to False.

Section 1.2: The Unique Else Clause

What differentiates Python's while loop from others is the option to incorporate an else clause. This else block runs when the condition in the while loop becomes False. This feature is particularly beneficial for executing specific actions after the loop has completed.

Learn how to harness the power of while loops in Python, including practical examples that demonstrate their utility.

Section 2.1: Example 1 - Countdown

Consider this practical example of a countdown:

count = 5

while count > 0:

print(count)

count -= 1

else:

print("Countdown complete!")

In this snippet, we start with a variable count set to 5 and reduce it by 1 with each iteration. Once the condition fails (count <= 0), the else block executes, displaying "Countdown complete!".

Section 2.2: Example 2 - Prime Number Check

Here’s another example that checks for prime numbers:

num = 10

is_prime = True

while num > 1:

if num % 2 == 0:

is_prime = False

break

num -= 1

else:

print("Prime number found!" if is_prime else "Not a prime number.")

In this case, the while loop checks if a number is prime by decrementing it and assessing for divisors. If no divisors are found, indicating the number is prime, the else block outputs "Prime number found!".

Best Practices and Tips

• Ensure that the condition in your while loop will eventually resolve to False to avoid infinite loops.
• Use the else clause thoughtfully to manage tasks after the loop completes without relying on extra flags or variables.
• Keep the code within the loop focused and succinct.