Comparator contracts

Questions 1 to 5 of 8

1. 1. A class defines __eq__ but no ordering method. What happens when sorted() runs on a list of its objects?

   It sorts the objects by their memory address, with no errorIt returns the list unchanged, because __eq__ is enough to order itemsIt raises TypeError with a message that < is not supported between instances of the classIt sorts by the result of __eq__, which is True or False
2. 2. What does this code do? ``python sorted([3, None, 1]) ``

   It sorts None to the front, with no errorIt raises TypeError, because < is not supported between None and intIt returns [1, 3, None] with None at the endIt drops the None value without an error
3. 3. What does this program print? ``python tasks = [(1, 2), (2, 2), (3, 1), (4, 2)] # (task id, priority) by_priority = {} for task_id, priority in tasks: by_priority[priority] = task_id print(len(by_priority)) ``

   4123
4. 4. What is the name of the contract rule that says the order must chain, so that if a comes before b and b comes before c, then a comes before c?

   Type your answer.

5. 5. A comparator returns -1 for both compare(a, b) and compare(b, a). Which contract rule does it break?

   Swapping the two items must flip the sign of the answerThe order must chain, so if a is before b and b is before c, then a is before cThe answer must not change between calls with the same two itemsEqual items must compare the same against every third item