A couple of methods used for building a neat password. passwords is a generator of random passwords using a specfic set of characters and a min and max length. valid_password is just one validation, you can certainly make up more requirements for what should pass as a valid password. This one is used to specify how many digits, lowercase and upp…

passwords.py

def password_generator(min_len= 10, max_len=18,
              chars='abcdefghjkmnpqrstauvz123456789ABCDEFGHIJKLMNOPQRSTUVXYZ!#$@'):
    "Generator of random passwords using the character set 'chars'"
    from random import randint
    length = randint(min_len,max_len)
    while True:
        yield ''.join(choice(chars) for i in range(length))


def valid_password(password, digits=0, lower_case=0, upper_case=0):
    """Returns true if there's more than 2 digits, more than 4 lowercase
    and more than 4 uppcase letters in a password"""

    count = lambda chars: sum(1 for char in password if char in chars)

    return (count('0123456789') >= digits and
            count('abcdefghijklmnopqrstuvwxyz') >= lower_case and
            count('ABCDEFGHIJKLMNOPQRSTUVwXYZ') >= upper_case)


def generate_password():
    "Returns a valid password with at least 2 digits, 2 upper and 2 lower case chars."
    return next(pw for pw in password_generator() if valid_password(pw, 2, 2, 2))