I am new to python and am trying to learn OOP. I have this mock up quiz that i have been trying to solve. So far am able to pass 5 test

Here is the challenge

Users come in 3 flavors, normal users, moderators, and admins. Normal users can only create new comments, and edit the their own comments. Moderators have the added ability to delete comments (to remove trolls), while admins have the ability to edit or delete any comment.
Users can log in and out, and we track when they last logged in
Comments

Encapsulation of Properties

All classes should have no publicly accessible fields
You should make sure you at least "hide" the required fields, for example, using _name instead of _name. Alternatively, feel free to use a better solution as extra credit.
The method-based API is provided. These must be completed as-is.
Additional methods are allowed, though remember to keep read-only properties read-only.
Instantiation

Classes should be instantiated with properties (as provided), to create instances with values already assigned.
User/Moderator/Admin defaults:
Should be marked as not logged in
Should return None for the last logged in at property
Comment defaults:
Should set the current timestamp for the created at property upon instantiation
Replied To is optional, and should be None if not provided.
Inheritance & Access Control

User
Users can be logged in and out.
When logging in, set the last_logged_in_at timestamp. Do not modify this timestamp when logging out
Users can only edit their own comments
Users cannot delete any comments
Moderator is a User
Moderators can only edit their own comments
Moderators can delete any comments
Admin is both a User and a Moderator
Admins can edit any comments
Admins can delete any comments
Composition

Comments contain a reference to the User who created it (author)
Comments optionally contain a reference to another comment (replied_to)
When converting to a string (to_string), the following format is used:
No replied to:
message + " by " + author.name
With replied to:
message + " by " + author.name + " (replied to " + repliedTo.author.name + ")"

this is my solution

import datetime

class user:



  def __init__(self, name, lastloggedIn = None):

    self.name = name

    self.loggedIn = False

    self.lastloggedIn = None



  def name(self):

    return self.name



  def name(self, value):

    self.name = value    



  def is_logged_in(self):

    return self.loggedIn



  def last_logged_in_at(self):

    return self.lastloggedIn



  def log_in(self):

    self.loggedIn = True

    self.lastloggedIn = datetime.datetime.utcnow()





  def log_out(self):

    self.loggedIn = False



  def can_edit(self, comment):

    if comment.author.name == self.name:

      return True

    else:

      return False



  def can_delete(self, comment):

    return False



#   def to_string(self):

#       pass



class moderator(user):

  def __init__(self, name):

    user.__init__(self, name)



  def can_delete(self, comment):

    return True







class admin(moderator):



  def __init__(self, name):

    moderator.__init__(self, name)



  def can_edit(self, comment):

    return True    





class comment:

  def __init__(self, author, message, replied_to = None, createdAt = None):

    self.createdAt = datetime.datetime.now()

    self.author = author

    self.message = message

    self.replied_to = replied_to



  def author(self):

    return self._author



  def author(self, value):

    self.author = value



  def message(self):

    return self.message



  def message(self, value):

      self.message = value



  def created_at(self):

      return self.createdAt



  def replied_to(self):

      return self.replied_to



  def replied_to(self, value):

      self.replied_to = value



  def to_string(self):

      if self.replied_to == None:

          return self.replied_to + " by " + self.author.name









import unittest



user1 = user('User 1')

mod = moderator('Moderator')



class Test(unittest.TestCase):

  def test_instantiation(self):

    self.assertEqual(user1.name,'User 1', 'User name is set correctly')

    user1.name = 'User 1 Updated'

    self.assertEqual(user1.name,'User 1 Updated', 'User name can be updated')

    self.assertIsInstance(mod, user, 'Moderator is a user')

Am getting two main errors. the last_logged_in method should return None and the datetime.datetime.now() doesn't seem to be working correctly

AssertionError: <bound method comment.created_at of <solution.comment object at 0x7fd5a21d0668>> is not an instance of <class 'datetime.datetime'>



AssertionError: <bound method user.last_logged_in_at of <[35 chars]ba8>> != None : Last logged in date is not set by default

Let's start with the first error:

AssertionError: <bound method comment.created_at of <solution.comment object at 0x7fd5a21d0668>> is not an instance of <class 'datetime.datetime'>

ITsays you are passing datetime instance. Let's check:

>>> import datetime

>>> datetime.datetime.now()

datetime.datetime(2018, 11, 21, 10, 28, 26, 996940) # this is datetime instance

what you can do is convert it to string and pass it:

>>> datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")

'2018-11-21 06:51:22'

Like:

class comment:

  def __init__(self, author, message, replied_to = None, createdAt = None):

    self.createdAt = datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")

For the second error:

AssertionError: <bound method user.last_logged_in_at of <[35 chars]ba8>> != None : Last logged in date is not set by default

You are not setting lastloggedIn:

 def __init__(self, name, lastloggedIn = None):

    self.name = name

    self.loggedIn = False

    self.lastloggedIn = lastloggedIn

and same here you are passing an instance:

>>> datetime.datetime.utcnow()

datetime.datetime(2018, 11, 21, 6, 46, 25, 248409)

change it to return the string instead of an instance:

 def log_in(self):

    self.loggedIn = True

    self.lastloggedIn = datetime.datetime.utcnow().strftime("%Y-%m-%d %H:%M:%S")