Advanced Password Strength Checker Python Script

#!/usr/bin/env python3
import re
import getpass

def evaluate_password_strength(password):
    """
    Evaluate the password strength based on five criteria:
    - At least 8 characters long
    - Contains an uppercase letter
    - Contains a lowercase letter
    - Contains a digit
    - Contains a special character
    Additionally, the function checks for commonly used (and easily guessable) passwords.
    Returns a tuple containing the strength rating, score, and suggestions for improvement.
    """
    score = 0
    suggestions = []

    # Check for common (easily guessable) passwords
    common_passwords = {
        "password", "12345", "123456", "qwerty", "abc123",
        "111111", "123123", "password1", "letmein", "admin"
    }
    if password.lower() in common_passwords:
        suggestions.append("Your password is among the most commonly used and easily guessable passwords. Please choose a more unique password.")
        # Override the score for common passwords
        score = 0
        # Early return the evaluation since it's a significant security risk.
        return "Weak", score, suggestions

    # Check for minimum length
    if len(password) >= 8:
        score += 1
    else:
        suggestions.append("Make sure your password is at least 8 characters long.")

    # Check for uppercase letters
    if re.search(r'[A-Z]', password):
        score += 1
    else:
        suggestions.append("Include at least one uppercase letter.")

    # Check for lowercase letters
    if re.search(r'[a-z]', password):
        score += 1
    else:
        suggestions.append("Include at least one lowercase letter.")

    # Check for digits
    if re.search(r'\d', password):
        score += 1
    else:
        suggestions.append("Include at least one digit.")

    # Check for special characters
    if re.search(r'[\W_]', password):
        score += 1
    else:
        suggestions.append("Include at least one special character.")

    # Determine strength rating based on the score
    if score <= 2:
        strength = "Weak"
    elif score in [3, 4]:
        strength = "Moderate"
    else:
        strength = "Strong"

    return strength, score, suggestions

def main():
    print("Password Strength Checker")
    # Using getpass to hide input for privacy; replace with input() if needed.
    password = getpass.getpass("Enter a password to evaluate: ")
    
    strength, score, suggestions = evaluate_password_strength(password)
    
    print(f"\nPassword Strength: {strength}")
    print(f"Score: {score} out of 5")
    
    if score == 5:
        print("\nExplanation: This password is strong because it meets all the required criteria: it is at least 8 characters long, includes both uppercase and lowercase letters, contains at least one digit, and has at least one special character.")
    elif suggestions:
        print("\nSuggestions for improvement:")
        for suggestion in suggestions:
            print(f" - {suggestion}")

if __name__ == '__main__':
    main()