How to Validate User Input in Python: Ensuring Numbers are Within Range

Learn how to effectively validate user input in Python by repeatedly asking for numbers until they fall within a specified range and ensure their sum meets a required total.
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Mastering User Input Validation in Python

Validating user input is a crucial part of programming, particularly when developed with Python. Whether you're creating a simple script or a robust application, the need to ensure that user inputs meet certain criteria is imperative. One common requirement is checking whether the input falls within a specified range and meets a specific condition, such as summing to a particular total. Let’s dive into how you can effectively manage this in Python.

The Problem at Hand

In your scenario, you want to prompt users to enter three numbers that should all be between 0 and 120. If a user enters an out-of-range number, the program should ask for that specific number again. Once all three numbers are provided, the program should check that their sum equals 120. If not, it should ask for the numbers again.

This could seem a bit complex if you're trying to implement it without properly structured looping and checks.

Solution Breakdown

To solve this problem, we'll implement a function that retrieves user input and checks if it's in range. We’ll then use this function to accept three numbers and ensure that they add up to the desired total. Here’s a step-by-step approach:

Step 1: Create an Input Function

First, we need a function that will repeatedly ask the user for input until they provide a valid number:

[[See Video to Reveal this Text or Code Snippet]]

Explanation:

Function Definition: We define a function called get_input, which takes an integer n as an argument to label the input.

While Loop: The loop continues until a valid input (between 0 and 120) is entered.

Input Prompt: We ask the user to provide their input, utilizing an f-string for clear and formatted prompts.

Step 2: Collect Inputs in a Loop

Next, we can utilize the input function within an overarching loop that continues to ask for numbers until the total is correct:

[[See Video to Reveal this Text or Code Snippet]]

Explanation:

Infinite Loop: We use a while True loop to ensure that our program continuously runs until the user successfully inputs correct values.

Collecting Numbers: Each call to get_input asks for a number and checks if it's within the defined range.

Final Check: After gathering all three numbers, it checks if the sum equals 120. If the sum does not match the expected value, it informs the user and prompts for all three numbers again.

Conclusion

The provided code accomplishes the task effectively by combining looping and function usage to validate user inputs and ensure they fit both range and summation requirements. Below is the complete code for reference:

[[See Video to Reveal this Text or Code Snippet]]

Final Thoughts

Validating user input is not only necessary but also enhances the reliability of your applications. Using the above structure, you can adapt the code for more complex user input checks. Remember, a little planning goes a long way in developing user-friendly applications!

If you have any questions on this topic or want further clarifications, feel free to ask! Happy coding!