The while loop in Python is used to execute a block of code as long as a condition is True.

Syntax

while condition:
   # code block

• The loop will continue to run as long as the condition is true.
• The condition is checked before each iteration.

Example 1: Basic while Loop

count = 1
while count <= 5:
   print(count)
   count += 1

Output:

1
2
3
4
5

Important: Infinite Loop

Be careful! If the condition never becomes False, the loop will run forever.

# WARNING: Infinite loop unless you stop it manually
while True:
   print("This will run forever")

Use break to stop such loops when needed.

Example 2: Loop Until User Input

password = ""
while password != "admin123":
   password = input("Enter password: ")
print("Access granted!")

Example 3: Countdown

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

Output:

5
4
3
2
1

Example 4: while with else

An optional else block runs after the loop ends normally (not by break).

i = 1
while i <= 3:
   print(i)
   i += 1
else:
   print("Loop finished!")

Output:

1
2
3
Loop finished!

Loop Control Statements in while

1. break – Exit the loop early

i = 1
while i <= 5:
   if i == 3:
       break
   print(i)
   i += 1

Output:

1
2

2. continue – Skip current iteration

i = 0
while i < 5:
   i += 1
   if i == 3:
       continue
   print(i)

Output:

1
2
4
5
3. pass – Do nothing

Used as a placeholder where code will be added later.

i = 0
while i < 3:
   pass  # do nothing
   i += 1

Real-world Use Case: Menu System

choice = ""
while choice != "q":
   print("1. Say Hello\nq. Quit")
   choice = input("Choose an option: ")
   if choice == "1":
       print("Hello!")

Summary Table

Exercise

Task: Use a while loop to print even numbers from 2 to 10.

num = 2
while num <= 10:
   print(num)
   num += 2

Output:

2
4
6
8
10