diff --git a/youngjin.han/learning-node02-2020.org b/youngjin.han/learning-node02-2020.org
index d2215f4..3c26201 100644
--- a/youngjin.han/learning-node02-2020.org
+++ b/youngjin.han/learning-node02-2020.org
@@ -1,3 +1,12 @@
+* 2020-06-12
+*** Python #9:
+**** DONE Lecture content
+     CLOSED: [2020-06-12 금 22:43]
+     - Same structure as "Python #2"
+     - Exercise 42
+     - Review all previous exercises, ensure you understand them
+**** Lecture material
+     - Available on https://cloud.ungleich.ch/s/435FyfrQyEq6oF3
 * 2020-06-10
 *** Python #8:
 **** DONE Lecture content
diff --git a/youngjin.han/python-the-hard-way/ex42.py b/youngjin.han/python-the-hard-way/ex42.py
new file mode 100644
index 0000000..f6341cc
--- /dev/null
+++ b/youngjin.han/python-the-hard-way/ex42.py
@@ -0,0 +1,94 @@
+## Animal is parents
+## Animal is-a object (yes, sort of confusing) look at the extra credit
+class Animal(object):
+    pass
+
+## Animal is parents and Dog is child
+## Dog is-a Animal and has-a __init__ that takes self and name parameters
+class Dog(Animal):
+
+    def __init__(self, name):
+        ## Dos has-a name
+        self.name = name
+
+## Animal is parents and Cat is child
+## Cat is-a Animal and has-a __init__ that takes self and name parameters
+class Cat(Animal):
+
+    def __init__(self, name):
+        ## Cat has-a name
+        self.name = name
+
+## Person is parents
+## Person is-a object and has-a __init__ that takes self and name parameters
+class Person(object):
+
+    def __init__(self, name):
+        ## Person has-a name
+        self.name = name
+
+        ## Person has-a pet of some kind
+        self.pet = None
+
+## Persion is parents and Employee is child
+## Employee is-a Person and has-a __init__ that takes self and name parameters
+class Employee(Person):
+
+    def __init__(self, name, salary):
+        ## ?? hmm what is this strange magic?
+        ## From super, get the __init__ function, and call it with parameters self, name
+        super(Employee, self).__init__(name)
+        ## Employee has-a salary
+        self.salary = salary
+
+## Fish is parents
+## Fish is-a object
+class Fish(object):
+    pass
+
+## Fish is parents and Salmon is child
+## Salmon is-a Fish
+class Salmon(Fish):
+    pass
+
+## Fish is parents and Halibut is child
+## Halibut is-a Fish
+class Halibut(Fish):
+    pass
+
+
+## Set rover to an instance of class Dog
+## rover is-a Dog that has-a name is-a Rover
+rover = Dog("Rover")
+
+## Set satan to an instance of class Cat
+## stan is-a cat that has-a name is-a Satan
+satan = Cat("Satan")
+
+## Set mary to an instance of class Person
+## mary is-a Person that has-a name is-a Mary
+mary = Person("Mary")
+
+## From mary, get the pet attribute, and set it to satan
+## mary's pet is-a cat that has-a name that is-a Satan
+mary.pet = satan
+
+## Set frank to an instance of class Employee
+## frank is-a Employee and salary is-a 120000
+frank = Employee("Frank", 120000)
+
+## From frank, get the pet attribute, and set it to rover
+## frank's pet is-a dog that has-a name that is-a Rover
+frank.pet = rover
+
+## Set flipper to an instance of class Fish
+## flipper is-a Fish
+flipper = Fish()
+
+## Set crouse to an instance of class Salmon
+## crouse is-a Salmon
+crouse = Salmon()
+
+## Set harry to an instance of class Halibut
+## harry is-a Halibut
+harry = Halibut()
diff --git a/youngjin.han/python.org b/youngjin.han/python.org
index cdfb9d9..2b24ffb 100644
--- a/youngjin.han/python.org
+++ b/youngjin.han/python.org
@@ -1,8 +1,11 @@
+* 2020-06-12
+  - ex42.py
+    - MRO(method resolution order)
 * 2020-06-10
 ** note
   - ex40.py
     - none
-  - ex40.py
+  - ex41.py
     - none
 * 2020-06-08
 ** note