old_contents: for i in [1, 2, 3, 4]:
      print(i)
  
  for i in range(5):
      print(i)
  
  
new_contents: for i in [1, 2, 3, 4]:
      print(i)
  
  for i in range(5):
      print(i)
  
  colors = ["red", "green", "blue"]
  for i in range(len(colors)):
      print(i, colors[i])
  
  for color in colors:
      print(color)
  
  for idx, color in enumerate(colors):
      print(idx, color)
  
  people = ["Scott", "John", "Mike"]
  ages = [50, 30, 25]
  for person, age in zip(people, ages):
      print(person, age)
  
  for data in zip(people, ages):
      print(data)
  
subject: Add more looping demos.