Understanding while Loops
What is a While Loop?
A while loop repeats a block of code as long as a given condition is True. It’s useful when the number of repetitions is not known in advance but depends on a condition.
How Does a While Loop Work?
Check the condition:
If True, execute the loop body.
If False, exit the loop.
Repeat until the condition becomes False.
Basic Syntax
while condition:
# Code to repeat
Example: Count from 1 to 5
count = 1
while count <= 5:
print(count)
count += 1
Output:
1
2
3
4
5
Flowchart of a While Loop
Start.
Evaluate the condition:
True: Execute the loop body.
False: Exit the loop.
Repeat steps until the condition becomes False.
End.
Important Points About While Loops
Infinite Loops: A while loop can run forever if the condition never becomes False.
Example:
while True:
print("This loop never ends!")
Solution: Ensure the condition changes inside the loop to eventually become False.
Breaking a Loop: Use break to exit a loop immediately.
Example:
while True:
print("Looping...")
break
Examples
Example 1: Countdown
number = 5
while number > 0:
print(number)
number -= 1
print("Blast off!")
Output:
5
4
3
2
1
Blast off!
Example 2: User Input
password = ""
while password != "python":
password = input("Enter the password: ")
print("Access granted!")
Example 3: Breaking a Loop
count = 0
while True:
print(count)
count += 1
if count == 3:
break
Output:
0
1
2
Practice Exercises
Exercise 1: Counting Up
Write a while loop that prints numbers from 1 to 10.
Exercise 2: Guess the Number
Write a program that asks the user to guess a number between 1 and 10. Keep asking until they guess it correctly.
Exercise 3: Sum of Numbers
Write a program that calculates the sum of numbers from 1 to 100 using a while loop.
Exercise 4: Multiplication Practice
Write a program that asks the user for a number and prints its multiplication table until they enter 0.
Exercise 5: Collect Items
Write a program that keeps asking the user to enter an item for their shopping list. Stop asking when they type "done."
Bonus Challenge
Write a program that:
Asks the user for their name and a number (e.g., 5).
Uses a while loop to print the user's name the specified number of times.
Congratulations!
You’ve learned how to use while loops in Python to repeat actions based on a condition. Practice these exercises to solidify your understanding and become more confident with loops! 🎉