Quick Check: Python Objects, Values, Types, and Identity

Review

1. Which expression asks whether two names refer to the same object?

   is tests object identity; == performs an equality comparison.
2. After items = [1, 2]; before = id(items); items.append(3), which statement is correct?

   append mutates the existing list object.
3. Why can a list not be used as a dictionary key?

   Dictionary keys must be hashable; mutable lists are unhashable.
4. Two separately created lists contain the same elements. Which result is normally true?

   Separate list objects can compare equal while remaining different objects.
5. Which is the intended identity test for the singleton None?

   None is a singleton object, so is is the appropriate identity test.