old_contents: # calculate
  print(1-2)
  print(4*5)
  print(7/5)
  print(3**2)
  
  # check type
  print(type(10))
  print(type(2.78))
  print(type("hello"))
  
  # use variable
  x = 10
  print(x)
  x = 100
  print(x)
  y = 3.14
  print(x*y)
  print(type(x*y))
  
  # list
  a = [1, 2, 3, 4, 5]
  print(a)
  print(len(a))
  print(a[0])
  print(a[4])
  a[4] = 99
  print(a)
  print(a[0:2])
  print(a[1:])
  print(a[:3])
  print(a[:-1])
  print(a[:-2])
  
new_contents: # calculate
  print(1-2)
  print(4*5)
  print(7/5)
  print(3**2)
  
  # check type
  print(type(10))
  print(type(2.78))
  print(type("hello"))
  
  # use variable
  x = 10
  print(x)
  x = 100
  print(x)
  y = 3.14
  print(x*y)
  print(type(x*y))
  
  # list
  a = [1, 2, 3, 4, 5]
  print(a)
  print(len(a))
  print(a[0])
  print(a[4])
  a[4] = 99
  print(a)
  print(a[0:2])
  print(a[1:])
  print(a[:3])
  print(a[:-1])
  print(a[:-2])
  
  # dictionary
  me = {'height': 180}
  print(me['height'])
  me['weight'] = 70
  print(me)
  
subject: Add python dictionary