How to check if a password is valid and matches a regular expression in Python

Question

I'm writing a function that sometimes will receive a massive calls (near 2k/minute) and it should check if the password is valid.

My requirements are simple:

• At least 5 characters;

• At least 1 number;

• At least 1 uppercase letter;

• At least 1 lowercase letter;

• At least 1 special character.

For now, I have code my function as:

import re

def check(p):

    return re.match(r"(?=.*\d)(?=.*[a-z])(?=.*[A-Z])(?=.*[^a-zA-Z0-9])(?!.*\s).{5}$", p)

I have some questions:

• Why my regex only works for 5 characters? If I try to validate a string with 6 characters, it fails.

• Isn't regex kinda slow during peak time? What are other alternatives?

Answer 1

The following should do the trick (note the {5,}):

re.match(r"(?=.*\d)(?=.*[a-z])(?=.*[A-Z])(?=.*[^a-zA-Z0-9])(?!.*\s).{5,}$", p)

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In other words, {5,} means 5 or more as opposed to {5} that means exactly 5.