Just to introduce with the app logic

algo.py

"""Password managing algorithm"""
import hashlib
import hmac
import bcrypt

class PasswordManager:
    _log_rounds = 12
    _prefix = '2b'
    _handle_long_passwords = False

    def _unicode_to_bytes(self, unicode_string):
        if isinstance(unicode_string, str):
            bytes_object = bytes(unicode_string, 'utf-8')
        else:
            bytes_object = unicode_string
        return bytes_object

    def generate_password_hash(self, password, rounds=None, prefix=None):
        if not password:
            raise ValueError('Password must be non-empty.')

        if rounds is None:
            rounds = self._log_rounds
        if prefix is None:
            prefix = self._prefix

        password = self._unicode_to_bytes(password)
        prefix = self._unicode_to_bytes(prefix)

        if self._handle_long_passwords:
            password = hashlib.sha256(password).hexdigest()
            password = self._unicode_to_bytes(password)

        salt = bcrypt.gensalt(rounds=rounds, prefix=prefix)
        return bcrypt.hashpw(password, salt)

    def check_password_hash(self, pw_hash, password):
        pw_hash = self._unicode_to_bytes(pw_hash)
        password = self._unicode_to_bytes(password)

        if self._handle_long_passwords:
            password = hashlib.sha256(password).hexdigest()
            password = self._unicode_to_bytes(password)

        return hmac.compare_digest(bcrypt.hashpw(password, pw_hash), pw_hash)