What is the "while" loop in Python and how to use it?

Question

Jayant Kumar · Accepted Answer

Table of Contants
Introduction:
A while loop in Python allows you to repeatedly execute a block of code as long as a specified condition is True. Unlike a for loop that runs a predefined number of times, a while loop continues until its condition becomes False. This makes it particularly useful when the number of iterations is not known in advance.
Syntax of the **while** Loop
The basic syntax of a while loop is:
while condition:
    # Code block to execute

**condition**: The loop will continue to execute as long as this condition evaluates to True.
The loop stops when the condition becomes False.

Example: Basic while Loop
counter = 1

while counter &#x3C;= 5:
    print(counter)
    counter += 1

The loop prints numbers from 1 to 5. The condition counter &#x3C;= 5 is checked before each iteration. Once counter becomes greater than 5, the loop stops.

Key Points:

Initialization: Typically, a variable is initialized before the while loop.
Condition: The loop runs while this condition remains True.
Update: Inside the loop, the variable controlling the condition is updated (e.g., counter += 1).

Practical Use Cases for the while Loop

Repeating Code Until a Condition is Met:

The while loop is ideal for cases where you don’t know in advance how many iterations you’ll need.
Example: Taking User Input Until a Valid Input is Received
password = ""

while password != "1234":
    password = input("Enter the password: ")
print("Access granted.")

The loop continues to ask for a password until the correct one ("1234") is entered.

Infinite Loops:

If the loop condition never becomes False, the loop will run indefinitely. Be cautious when writing while loops to avoid infinite loops unless they're intentional.
Example: Creating an Infinite Loop
while True:
    print("This will run forever.")

This loop will run continuously because the condition True is always satisfied.

Controlling a while Loop: break and continue
1. **break** Statement:
The break statement allows you to exit the loop immediately, regardless of the loop condition.
Example: Exiting a Loop with break
count = 0

while count &#x3C; 10:
    if count == 5:
        break
    print(count)
    count += 1

The loop prints numbers from 0 to 4. When count reaches 5, the loop terminates because of the break statement.

2. **continue** Statement:
The continue statement skips the rest of the loop's current iteration and moves on to the next one.
Example: Skipping an Iteration with continue
count = 0

while count &#x3C; 5:
    count += 1
    if count == 3:
        continue
    print(count)

The loop skips printing the number 3 by using continue, but continues with the next iteration.

Using else with a while Loop
Python allows an else block to be used with a while loop. The else block is executed when the loop condition becomes False naturally, not when the loop is exited via break.
Example:
count = 0

while count &#x3C; 3:
    print(count)
    count += 1
else:
    print("Loop finished.")

The else block executes after the loop completes, printing "Loop finished."

Practical Examples of Using the while Loop
1. Factorial Calculation:
You can use a while loop to calculate the factorial of a number.
n = 5
factorial = 1

while n > 0:
    factorial *= n
    n -= 1
print(f"Factorial is {factorial}")

The loop multiplies factorial by n until n becomes 0. The result is 5! = 120.

2. Guessing Game:
A while loop is great for repeating actions until a specific condition is met.
import random

number = random.randint(1, 10)
guess = 0

while guess != number:
    guess = int(input("Guess the number between 1 and 10: "))
    if guess &#x3C; number:
        print("Too low!")
    elif guess > number:
        print("Too high!")
print("Congratulations! You guessed it.")

This loop continues asking the user to guess the number until they guess correctly.

Conclusion:
The while loop in Python is a powerful control structure that allows for repeated execution of a block of code as long as a condition is True. Whether used for user input, calculations, or even infinite loops, while loops provide flexibility in situations where the number of iterations isn't predetermined. By combining it with statements like break and continue, you can effectively manage loop control and improve the efficiency of your programs.

What is the "while" loop in Python and how to use it?

Table of Contants

Introduction:

Example: Basic `while` Loop

Key Points:

Practical Use Cases for the `while` Loop

Example: Taking User Input Until a Valid Input is Received

Example: Creating an Infinite Loop

Controlling a `while` Loop: `break` and `continue`

1. `break` Statement:

Example: Exiting a Loop with `break`

2. `continue` Statement:

Example: Skipping an Iteration with `continue`

Using `else` with a `while` Loop

Example:

Practical Examples of Using the `while` Loop

1. Factorial Calculation:

2. Guessing Game:

Conclusion:

Similar Questions