👀 Views: 0 💬 Answers: 1 📅 Created: 2025-08-24

regex python password-validation Python

I'm migrating some code and Could someone explain This might be a silly question, but I'm trying to create a regex pattern in Python to validate user passwords based on specific criteria... The requirements are that the password must be at least 8 characters long, contain at least one uppercase letter, one lowercase letter, one digit, and one special character from the set `!@#$%^&*()`. Additionally, the password should not have any spaces and must not be longer than 16 characters. However, I’m running into an scenario where passwords that are 8 characters long with all required characters are sometimes being rejected. Here's the regex pattern I've come up with so far: ```python import re pattern = r'^(?=.*[A-Z])(?=.*[a-z])(?=.*[0-9])(?=.*[!@#$%^&*()])(?=.{8,16}$)[^\s]*$' ``` I've tested the regex against a few passwords, but I keep getting the following behavior message for valid passwords: `re.behavior: nothing to repeat`. This behavior doesn't seem to correlate with my test cases directly. Here’s an example of a password I’m trying to validate: ```python password = 'P@ssw0rd1' if re.match(pattern, password): print('Valid Password') else: print('Invalid Password') ``` Despite satisfying all the criteria, it returns `Invalid Password`. I've also tried to simplify my regex to isolate the question, but it keeps failing for various cases. Can someone guide to identify what's wrong with my regex or suggest an alternative approach? Also, are there best practices to ensure that the performance of regex checks remains optimal, especially when validating multiple passwords in bulk? I'm working on a CLI tool that needs to handle this. Has anyone else encountered this? I recently upgraded to Python latest. The stack includes Python and several other technologies. I'm open to any suggestions.