Скачать или смотреть How to Fix Your While Loop Not Printing Output in Python

Learn how to properly structure your while loop and if statement in Python when checking user input for a PIN. This guide provides easy-to-follow steps to solve common issues!
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This video is based on the question https://stackoverflow.com/q/74766134/ asked by the user 'FennTheFern' ( https://stackoverflow.com/u/20627571/ ) and on the answer https://stackoverflow.com/a/74766150/ provided by the user 'user2182349' ( https://stackoverflow.com/u/2182349/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Troubleshooting Python: Making Your While Loop Work with If Statements

If you've ever tried to code a simple user input scenario in Python, you know it can sometimes lead you to a frustrating dead end. In this post, we will address a common issue one programmer faced while working on a PIN validation code.

The Problem

Consider the following code snippet that’s designed to validate a user’s PIN:

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

When executed, this code is meant to repeatedly prompt the user until they enter the correct PIN (1234). If the user inputs the correct PIN, the program should print "PIN accepted!". However, the user discovered that when they typed in the correct PIN, there was no output response, which is both confusing and frustrating.

The Underlying Issue

The main issue here is related to the placement of the if statement. The current structure of the loop only allows the if statement to run when the input is incorrect and the loop is still executing. This means that the first time the correct PIN (1234) is entered, it never reaches the if condition because the loop stops.

The Solution

To resolve this issue, we need to move the if statement outside of the while loop. This structure ensures that once the user enters the correct PIN and breaks out of the loop, we still get to check the PIN and provide an appropriate response.

Here’s how you should modify the code:

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

Explanation of the Fix

Understanding the While Loop: The while loop correctly checks if the entered PIN is not equal to 1234. If it isn't, it prompts the user again.

Checking After Exiting the Loop:

Moving the check for the correct PIN to after the loop allows you to validate the final input when the loop condition is no longer met.

By placing the if pin == 1234: statement outside of the loop, once the user enters the correct PIN, you will effectively exit the loop and then check the if condition.

Conclusion

By adjusting the placement of your if statement outside of the while loop, you ensure that your program gives feedback for valid input. This simple change not only resolves the immediate issue but also improves the overall structure of your code, making it clearer and more maintainable.

Now that you know the fix, give it a try!