How Can I Request and Validate User Input Reliably in My Program?

Requesting Valid User Input Until Provided

When developing programs that rely on user input, it is essential to handle situations where users provide invalid data. Instead of crashing or accepting inaccurate values, it is desirable to continuously prompt the user until a valid response is provided.

Using a While Loop with Try-Except

One approach to handle invalid user input efficiently involves enclosing the input method within a while loop. Utilize the try-except block to detect exceptions that arise when parsing user input. If an exception occurs, you can display an informative error message and continue the loop to prompt for valid input.

Implementing Custom Validation Logic

In scenarios where the required validation rules cannot be met by the default parsing methods, you can add custom validation logic within the while loop. Perform checks on the provided input and continue the loop if it does not meet the specified criteria.

Combining Exception Handling and Custom Validation

To accommodate both exception handling and custom validation effectively, consider combining both techniques within the while loop. This ensures that both anticipated and unanticipated input errors are caught, providing a more robust solution.

Encapsulating the Functionality

For greater code reuse when requesting user input multiple times, encapsulate the core functionality into a dedicated function. This simplifies calling the function multiple times with different prompts and validation rules.

A Practical Solution

To ensure that users provide valid input, consider implementing a sanitised_input function that accepts parameters such as the input prompt, expected data type, minimum and maximum acceptable values, and a range of allowed values. It returns the validated input only when it meets the specified criteria.

Common Pitfalls to Avoid

• Repetitive Input Statements: While it may seem convenient, using multiple input statements for validation can lead to inconsistencies and potential bugs.
• Stack Overflow with Recursion: Using recursion for input validation can cause a stack overflow if excessive errors occur. Stick to loops for reliability.

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