text: #!/usr/bin/env python3
  """Example of a decorator that adds a _created_at attribute to
  every instance created by the decorated class.
  
  From Reuven Lerner's "Practical Decorators" talk at PyCon 2019.
  Reuven's courses, books, and newsletter are at https://lerner.co.il/
  https://youtu.be/MjHpMCIvwsY
  """
  
  import time
  
  
  def object_birthday(c):
      def wrapper(*args, **kwargs):
          o = c(*args, **kwargs)
          o._created_at = time.time()
          return o
      return wrapper
  
  
  @object_birthday
  class Foo():
      def __init__(self, x, y):
          self.x = x
          self.y = y
  
  
  f = Foo(10, [10, 20, 30])
  print(f)
  print(f._created_at)
  