text: # assertions.py
  mylist = [1, 2, 3]  # pretend this comes from an external source
  
  assert 4 == len(mylist)  # this will break
  
  for position in range(4):
      print(mylist[position])
  
  
  """
  $ python assertions.py
  Traceback (most recent call last):
    File "assertions.py", line 4, in <module>
      assert 4 == len(mylist)  # this will break
  AssertionError
  """
  
  # asserts with message
  assert 4 == len(mylist), f"Mylist has {len(mylist)} elements"
  
  
  """
  $ python assertions.py
  Traceback (most recent call last):
    File "assertions.py", line 19, in <module>
      assert 4 == len(mylist), f"Mylist has {len(mylist)} elements"
  AssertionError: Mylist has 3 elements
  """
  