Understanding while Loop in Python
The while loop in Python repeatedly executes a block of code as long as a given condition is True. It’s useful when the number of iterations is not known in advance.
Basic Syntax
while condition:
# code to execute repeatedly
Let’s explore the while loop with practical examples to understand its power and flexibility.
Example 1: Simple Counter
i = 0
while i < 5:
print("Count:", i)
i += 1This prints numbers from 0 to 4.
Example 2: Waiting for a Condition
ready = False
attempts = 0
while not ready and attempts < 3:
print("Trying...")
attempts += 1
if attempts == 3:
ready = TrueLoops until either ready is True or attempts reach 3.
Example 3: User Input Loop
command = ""
while command != "exit":
command = input("Type 'exit' to quit: ")
print("You typed:", command)Keeps asking for input until user types 'exit'.
Example 4: Infinite Loop with Break
while True:
response = input("Continue? (y/n): ")
if response == "n":
breakCreates an infinite loop until the user decides to break it.
Example 5: Countdown
count = 5
while count > 0:
print("Countdown:", count)
count -= 1Counts down from 5 to 1.
Example 6: Skipping Iterations with Continue
num = 0
while num < 5:
num += 1
if num == 3:
continue
print(num)Skips printing the number 3.
Example 7: Using else with while
x = 0
while x < 3:
print("x is", x)
x += 1
else:
print("Loop finished")The else block executes after normal loop completion.
Example 8: Validating a Password
password = ""
while not password:
password = input("Enter password: ")
print("Password set")Prompts until the user enters a non-empty password.
Example 9: Searching for an Item
items = [3, 8, 12, 7, 9]
i = 0
while i < len(items):
if items[i] == 12:
print("Found at index", i)
break
i += 1Searches for the number 12 in the list.
Example 10: Loop With Multiple Conditions
balance = 100
withdrawal = 20
while balance >= withdrawal:
balance -= withdrawal
print("Remaining:", balance)Withdraws until the balance is insufficient.
When to Use while Loops
- When the number of iterations is not fixed.
- When waiting for a condition to become true.
- When repeatedly validating input or system status.
The while loop is a powerful way to build logic that adapts based on real-time conditions. With proper safeguards, it can make your Python programs smarter and more interactive.
