Methods

[buran]

this one

# a method to determine if the book is long (500 or more pages)
def is_long(self):
  if self.pages > 500:
      return True
  return False

is more or less correct, i.e. it could be done better, e.g.

# a method to determine if the book is long (500 or more pages)
def is_long(self):
  return self.pages >= 500

as to this one:

# a method to mark the book as completed
def mark_completed(self):
  if self.status == "c"
      self.title += "Mark as completed"
  elif self.status == "r"
      self.title += "Book is not completed"

I think you need to change status property and not change the book title.