Python study about class

add__slots__.py

class HpError(Exception):
  pass

class Employee(object):
  __slots__ = ['__name','__hp']
  def __init__(self,name,hp):
    self.__name=name
    self.__hp=hp

  def work(self,time):
    if self.__hp >= time:
      self.__hp -= time
    else:
      raise HpError

  def workable(self):
    if self.__hp > 0:
      return True
    else:
      return False

  def __sethp(self,hp):
    if hp >= 0:
      self.__hp=hp
    else:
      raise HpError

  def __gethp(self):
    return self.__hp

  hp=property(__gethp,__sethp)

first.py

class HpError(Exception):
  pass

class Employee(object):
  def __init__(self,name,hp):
    self.__name=name
    self.__hp=hp

  def work(self,time):
    if self.__hp >= time:
      self.__hp -= time
    else:
      raise HpError

  def workable(self):
    if self.__hp > 0:
      return True
    else:
      return False

  def sethp(self,hp):
    if hp >= 0:
      self.__hp=hp
    else:
      raise Exception

  def gethp(self):
    return self.__hp

  hp=property(gethp,sethp)

test.py

import unittest

class TestEmployee(unittest.TestCase):

  def setUp(self):
    self.employee = Employee("taro",100)

  def test_gethp(self):
    self.assertTrue(self.employee.hp == 100)

  def test_sethp(self):
    self.employee.hp=95
    self.assertTrue(self.employee.hp == 95)

  def test_sethp_error(self):
    try:
      self.employee.hp = -1
    except Exception:
      pass
    except e:
       self.fail('Unexpected exception thrown:', e)
    else:
       self.fail('ExpectedException not thrown')

  def test_work(self):
    self.employee.work(10)
    self.assertTrue(self.employee.hp == 90)

  def test_work_error(self):
    self.assertRaises(HpError,self.employee.work,200)

  def test_workable(self):
    self.employee.hp = 1
    self.assertTrue(self.employee.workable())

  def test_workable_false(self):
    self.employee.hp = 0
    self.assertFalse(self.employee.workable())

if __name__ == '__main__':

  unittest.main()

using__getattr__and__setattr__.py

#using __getattr__  __setattr__
class HpError(Exception):
  pass

class Employee(object):

  def __init__(self,name,hp):
    self.name=name
    self.hp=hp

  def work(self,time):
    if self.hp >= time:
      self.hp -= time
    else:
      raise HpError

  def workable(self):
    if self.hp > 0:
      return True
    else:
      return False

  def __setattr__(self,name,value):
    if name=='hp':
      self.__check_hp(value)
    self.__dict__[name]=value

  def __getattr__(self,name):
    return self.__dict__[name]

  def __check_hp(self,hp):
    if hp < 0:
      raise HpError