Question

Write an input validation loop that asks the user to enter "Yes" or "No".

Short answer

Question: Write a program that prompts the user to enter "Yes" or "No" and keeps asking until they enter a valid input. Answer: ```python user_input = input("Please enter 'Yes' or 'No': ") while user_input not in ["Yes", "No"]: print("Invalid input. Please try again.") user_input = input("Please enter 'Yes' or 'No': ") print("You've entered a valid input:", user_input) ```

Step-by-step solution

Ask the user for input

Begin by asking the user to enter "Yes" or "No" using the input() function. Store the user's input in a variable (e.g. user_input).

Create a while loop

Create a while loop that continues to run as long as the user input is not "Yes" or "No". To do this, use a while statement along with the not in keyword to check if the user input is valid.

Inside the loop, prompt the user for input again

Inside the while loop, print a message letting the user know their input was invalid. Then, prompt the user for input again using the input() function and store the new input in the user_input variable.

End the loop when valid input is received

The loop will continue to run until the user enters a valid input of either "Yes" or "No". Once that happens, the loop condition will be false and the loop will exit. Here's the code implementing these steps: ```python # Step 1: Ask the user for input user_input = input("Please enter 'Yes' or 'No': ") # Step 2: Create a while loop while user_input not in ["Yes", "No"]: # Step 3: Inside the loop, prompt the user for input again print("Invalid input. Please try again.") user_input = input("Please enter 'Yes' or 'No': ") # Step 4: End the loop when valid input is received print("You've entered a valid input:", user_input) ```

Key concepts

Python Programming

Python is a versatile and popular programming language known for its simplicity and readability, making it an excellent choice for beginners and professionals alike. At its core, Python uses a simple syntax that closely resembles the English language, which helps programmers write clear and logical code.

Python supports multiple programming paradigms, including procedural, object-oriented, and functional programming. It comes with a vast standard library, known for handling various tasks such as file I/O, string operations, and system-related functions. Additionally, Python has a rich ecosystem of third-party libraries for data science, machine learning, web development, automation, and more. This makes it easy for programmers to extend Python's capabilities to suit their needs.

In this exercise, we'll focus on Python's basic input and loop constructs, which are essential to understanding how to interact with users and process repetitive tasks.

While Loop

A while loop in Python continuously executes a block of code as long as a specific condition remains true. This makes it perfect for situations where you might not know in advance how many times you need to repeat an action. Instead, the loop will keep running based on the specified condition.

Here's how a while loop works:

• It evaluates a Boolean expression (condition).
• If the condition is true, the loop's code block is executed.
• Once the code block runs, the condition is checked again.
• If the condition remains true, it repeats the process. It stops when the condition is false.

In the context of the input validation exercise, the while loop is employed to repeatedly ask for user input until valid data is provided. Python’s ease of use in structuring loops maps well with real-world logic, promoting intuitive problem-solving.

User Input

User input in Python can be collected using the `input()` function, which reads a line from input, typically from the user. The function captures the data entered by the user as a string and can prompt users with a specific message to guide input collection.

For example: user_input = input("Enter your response: "). This command waits for the user to type something and then stores it in the `user_input` variable as a string. Processing user input is crucial for creating interactive programs that respond dynamically to inputs.

In this exercise, obtaining user input is the first step. After that, the input is compared against expected valid responses, in this case, "Yes" or "No". It's essential to anticipate and handle various inputs to prevent errors and ensure smooth user experience.

Validation Loops

Validation loops are essential programming constructs that check the validity of user input or data before processing. In Python, you can easily validate input using loops – particularly the while loop.

A validation loop repeatedly prompts the user for input until a correct value is provided. This ensures that the input meets specific criteria, like format or type. By comparing the input with expected valid values, you can prompt users accordingly when their input doesn't match the requirements, making programs more robust and user-friendly.

In the exercise, input validation is achieved using a while loop that checks whether the user's input is either "Yes" or "No". If it isn't, the loop prompts the user again, displaying an error message. This approach effectively manages incorrect inputs by ensuring valid responses before proceeding, thereby reducing potential errors and enhancing program reliability.