Python - Create CredFile to encode secrets locally

 from cryptography.fernet import Fernet

import re
import ctypes
import time
import os
import sys


class Credentials():

    def __init__(self):
        self.__username = ""
        self.__key = ""
        self.__password = ""
        self.__key_file = 'key.key'
        self.__time_of_exp = -1

    # ----------------------------------------
    # Getter setter for attributes
    # ----------------------------------------

    @property
    def username(self):
        return self.__username

    @username.setter
    def username(self, username):
        while (username == ''):
            username = input('Enter a proper User name, blank is not accepted:')
        self.__username = username

    @property
    def password(self):
        return self.__password

    @password.setter
    def password(self, password):
        self.__key = Fernet.generate_key()
        f = Fernet(self.__key)
        self.__password = f.encrypt(password.encode()).decode()
        del f

    @property
    def expiry_time(self):
        return self.__time_of_exp

    @expiry_time.setter
    def expiry_time(self, exp_time):
        if (exp_time >= 2):
            self.__time_of_exp = exp_time

    def create_cred(self):
        """
        This function is responsible for encrypting the password and create  key file for
        storing the key and create a credential file with user name and password
        """

        cred_filename = 'CredFile.ini'

        with open(cred_filename, 'w') as file_in:
            file_in.write("#Credential file:\nUsername={}\nPassword={}\nExpiry={}\n"
                          .format(self.__username, self.__password, self.__time_of_exp))
            file_in.write("++" * 20)

        # If there exists an older key file, This will remove it.
        if (os.path.exists(self.__key_file)):
            os.remove(self.__key_file)

        # Open the Key.key file and place the key in it.
        # The key file is hidden.
        try:

            os_type = sys.platform
            if (os_type == 'linux'):
                self.__key_file = '.' + self.__key_file

            with open(self.__key_file, 'w') as key_in:
                key_in.write(self.__key.decode())
                # Hidding the key file.
                # The below code snippet finds out which current os the script is running on and does the task base on it.
                if (os_type == 'win32'):
                    ctypes.windll.kernel32.SetFileAttributesW(self.__key_file, 2)
                else:
                    pass

        except PermissionError:
            os.remove(self.__key_file)
            print("A Permission error occurred.\n Please re run the script")
            sys.exit()

        self.__username = ""
        self.__password = ""
        self.__key = ""
        self.__key_file


def main():
    # Creating an object for Credentials class
    creds = Credentials()

    # Accepting credentials
    creds.username = input("Enter UserName:")
    creds.password = input("Enter Password:")
    print("Enter the epiry time for key file in minutes, [default:Will never expire]")
    creds.expiry_time = int(input("Enter time:") or '-1')

    # calling the Credit
    creds.create_cred()
    print("**" * 20)
    print("Cred file created successfully at {}"
          .format(time.ctime()))

    if not (creds.expiry_time == -1):
        os.startfile('expire.py')

    print("**" * 20)


if __name__ == "__main__":
    main()