how to check if a string fullfil with multiple regex and capture that portion that match?

What I want

I’m working with a django form and it takes a password input. I need to pass the input value for multiple regexes, which will test if:

• at least one character is a lowecase
• at least one character is a uppercase
• at least one character is a number
• at least one character is a especial character (symbol)
• 8 characters minimum

And I would like to know which of these conditions were fulfilled and which were not.

What I’ve done

def clean_password(self):
        password = self.cleaned_data.get("password")

        regexes = [
            "[a-z]",
            "[A-Z]",
            "[0-9]",
            #other regex...
        ]

        # Make a regex that matches if any of our regexes match.
        combined = "(" + ")|(".join(regexes) + ")"

        if not re.match(combined, password):
            print("Some regex matched!")
            
            # i need to pass in ValidationError those regex that haven't match
            raise forms.ValidationError('This password does not contain at least one number.')

Answer

While you can use a regex here, I would stick to normal Python:

from string import ascii_uppercase, ascii_lowercase, digits, punctuation
from pprint import pprint

character_classes = {'lowercase letter': ascii_lowercase,
                     'uppercase letter': ascii_uppercase,
                     'number': digits,
                     'special character': punctuation  # change this if your idea of "special" characters is different
                    }

minimum_length = 8

def check_password(password):
    long_enough = len(password) >= minimum_length
    if not long_enough:
        print(f'Your password needs to be at least {minimum_length} characters long!')
    result = [{class_name: char in char_class for class_name, char_class in character_classes.items()} for char in password]
    result_transposed = {class_name: [row[class_name] for row in result] for class_name in character_classes}
    for char_class, values in result_transposed.items():
        if not any(values):
            # Instead of a print, you should raise a ValidationError here
            print(f'Your password needs to have at least one {char_class}!')

    return result_transposed                      

check_password('12j3dSe')

Output:

Your password needs to be at least 8 characters long!
Your password needs to have at least one special character!

This allows you to modify the password requirements in a more flexible fashion, and in case you ever want to say “you need X of this character class”…