Python While Loop

The while loop is a control structure in Python that allows you to repeatedly execute a block of code as long as a certain condition is true. It is used when you want to repeat a set of instructions until the specified condition becomes false. Let's explore the syntax and usage of the while loop in Python with examples.

Syntax

The basic syntax of a while loop in Python is as follows:

    while condition:
    # Code to execute while the condition is true
  

Example 1: Printing Numbers

Consider the following example:

    num = 1

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

In this example, we initialize the variable "num" to 1. The while loop continues executing as long as the condition "num <= 5" is true. Inside the loop, we print the current value of "num" and then increment it by 1. The loop repeats until the value of "num" becomes 6, at which point the condition becomes false, and the loop terminates.

Example 2: Summing Numbers

You can also use a while loop to perform calculations. Here's an example that calculates the sum of numbers from 1 to 10:

    num = 1
sum = 0

while num <= 10:
    sum += num
    num += 1

print("The sum is:", sum)
  

In this example, we initialize "num" to 1 and "sum" to 0. Inside the while loop, we add the current value of "num" to "sum" and then increment "num" by 1. The loop continues until "num" reaches 11. After the loop terminates, we print the final value of "sum," which is the sum of numbers from 1 to 10.

Example 3: User Input

You can use a while loop to repeatedly prompt the user for input until a specific condition is met. Here's an example:

    password = ""

while password != "secret":
    password = input("Enter the password: ")

print("Access granted!")
  

In this example, the while loop continues as long as the value of "password" is not equal to "secret". Inside the loop, the user is prompted to enter a password using the input() function. If the entered password is not "secret", the loop repeats the prompt. Once the user enters the correct password, the loop terminates, and "Access granted!" is printed.

Conclusion

The while loop is a powerful construct in Python that allows you to repeat a block of code until a certain condition is false. By understanding the syntax and usage of the while loop, you can create dynamic and interactive programs that perform repetitive tasks efficiently.