The infinite loop
We can create an infinite loop using
while statement. If the condition of
while loop is always
True, we get an infinite loop.
Example of infinite loop
# An example of infinite loop # press Ctrl + c to exit from the loop while True: num = int(input("Enter an integer: ")) print("The double of",num,"is",2 * num)
Enter an integer: 3 The double of 3 is 6 Enter an integer: 5 The double of 5 is 10 Enter an integer: 6 The double of 6 is 12 Enter an integer: Traceback (most recent call last):
Loop with condition at the top
This is a normal
while loop without
break statements. The condition of the
while loop is at the top and the loop terminates when this condition is
Flowchart of Loop With Condition at Top
# Program to illustrate a loop with condition at the top n = int(input("Enter n: ")) # initialize sum and counter sum = 0 i = 1 while i <= n: sum = sum + i i = i+1 # update counter # print the sum print("The sum is",sum)
Enter n: 10 The sum is 55
Loop with condition in the middle
This kind of loop can be implemented using an infinite loop along with a conditional break in between the body of the loop.
Flowchart of Loop with Condition in Middle
# Program to illustrate a loop with condition in the middle. # Take input from the user untill a vowel is entered vowels = "aeiouAEIOU" # infinite loop while True: v = input("Enter a vowel: ") # condition in the middle if v in vowels: break print("That is not a vowel. Try again!") print("Thank you!")
Enter a vowel: r That is not a vowel. Try again! Enter a vowel: 6 That is not a vowel. Try again! Enter a vowel: , That is not a vowel. Try again! Enter a vowel: u Thank you!
Loop with condition at the bottom
This kind of loop ensures that the body of the loop is executed at least once. It can be implemented using an infinite loop along with a conditional break at the end. This is similar to the
do...while loop in C.
Flowchart of Loop with Condition at Bottom
# Python program to illustrate a loop with condition at the bottom # Roll a dice untill user chooses to exit # import random module import random while True: input("Press enter to roll the dice") # get a number between 1 to 6 num = random.randint(1,6) print("You got",num) option = input("Roll again?(y/n) ") # contion if option == 'n': break
Press enter to roll the dice You got 1 Roll again?(y/n) y Press enter to roll the dice You got 5 Roll again?(y/n) n