>>> class User():
...     def __init__(self):
...         self.username = 'PyWombat'
...         self.password = '123'
...
>>> user = User()

>>> user.email = 'pywombat@example.com'
>>> vars(user)

{'username': 'PyWombat', 'password': '123', 'email': 'pywombat@example.com'}