diff --git a/.gitignore b/.gitignore
index 3cfcda7..87f4579 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,3 @@
-/youngjin.han/dot-cdist/type/__my_computer/manifest~
-/youngjin.han/cdist.org~
-/youngjin.han/dot-cdist/type/__colourful_file/file/colourful~
-/youngjin.han/dot-cdist/type/__colourful_file/manifest~
-/youngjin.han/dot-cdist/type/__all_in_one/manifest~
+manifest~
 *.py~
+*.org~
diff --git a/youngjin.han/python-the-hard-way/ex3-1.py b/youngjin.han/python-the-hard-way/ex3-1.py
new file mode 100644
index 0000000..b661883
--- /dev/null
+++ b/youngjin.han/python-the-hard-way/ex3-1.py
@@ -0,0 +1,9 @@
+f_pi = 3.14159265358979
+
+print("org =", f_pi)
+print("trans format 1 = %.2f" % f_pi)
+print("trans format 2 =", round(f_pi, 2))
+print("trans format 3 = %.2f" % round(f_pi, 2))
+print("trans format 4 = {:.2f}".format(f_pi))
+print("trans format 5 = {:.2f}".format(round(f_pi, 2)))
+print("trans format 6 = {:.15f}".format(round(f_pi, 2)))
diff --git a/youngjin.han/python-the-hard-way/ex3-2.py b/youngjin.han/python-the-hard-way/ex3-2.py
new file mode 100644
index 0000000..dd88dfd
--- /dev/null
+++ b/youngjin.han/python-the-hard-way/ex3-2.py
@@ -0,0 +1,4 @@
+print((2**8) - 1)
+print((2**16) - 1)
+print((2**32) - 1)
+print((2**64) - 1)
diff --git a/youngjin.han/python-the-hard-way/ex3.py b/youngjin.han/python-the-hard-way/ex3.py
new file mode 100644
index 0000000..1276637
--- /dev/null
+++ b/youngjin.han/python-the-hard-way/ex3.py
@@ -0,0 +1,21 @@
+print("Hens", 25 + 30 / 6) # 25 + (30 / 6) = 25 + 5 = 30
+
+print("Roosters", 100 - 25 * 3 % 4) # 100 - (25 * 3 % 4) = 100 - (75 % 4) = 100 - 3 = 97
+print("Now I will count the eggs:") # print syntex
+
+print(3 + 2 + 1 - 5 + 4 % 2 - 1 / 4 + 6) # 3 + 2 + 1 - 5 + 0 - 0.25 + 6 = 6.75
+
+print("Is it true that 3 + 2 < 5 - 7?") # print syntex
+
+print(3 + 2 < 5 - 7) # 5 < -2 => false
+
+print("What is 3 + 2?", 3 + 2) # 5
+print("What is 5 - 7?", 5 - 7) # -2
+
+print("Oh, that's why it's False.") # print syntex
+
+print("How about some more.") # print syntex
+
+print("Is it greater?", 5 > -2) # true
+print("Is it greater or equal?", 5 >= -2) # true
+print("Is it less or equal?", 5 <= -2) # false
diff --git a/youngjin.han/python-the-hard-way/ex4.py b/youngjin.han/python-the-hard-way/ex4.py
new file mode 100644
index 0000000..203574b
--- /dev/null
+++ b/youngjin.han/python-the-hard-way/ex4.py
@@ -0,0 +1,17 @@
+cars = 100 # amount of car
+space_in_a_car = 4.0 # amount of seats in the car
+drivers = 30 # amount of driver
+passengers = 90 # amount of passenger
+cars_not_driven = cars - drivers # amount of person which could not drive = 70
+cars_driven = drivers # amount of person which could drive = 30
+carpool_capacity = cars_driven * space_in_a_car # amount of seat for carpool = 120
+average_passengers_per_car = passengers / cars_driven # 3
+
+
+print("There are", cars, "cars available.")
+print("There are only", drivers, "drivers available.")
+print("There will be", cars_not_driven, "empty cars today.")
+print("We can transport", carpool_capacity, "people today.")
+print("We have", passengers, "to carpool today.")
+print("We need to put about", average_passengers_per_car,
+         "in each car.")
diff --git a/youngjin.han/python.org b/youngjin.han/python.org
new file mode 100644
index 0000000..626f3d1
--- /dev/null
+++ b/youngjin.han/python.org
@@ -0,0 +1,11 @@
+* 2020-05-18
+** note
+   - ex1.py
+     - # is commnet.
+   - ex2.py
+     - I do't find mistakes.
+   - ex3.py
+     - none
+   - ex4.py
+     - car_pool_capacity is not defined.
+