Question 1

You can use a for loop on any collection.

Accepted Answer

A for loop can be used on any collection such as lists, tuples, dictionaries, sets, etc.

Question 2

Once the designer of a collection class has obtained its interface, the implementation of the class includes completing code for the methods.

Accepted Answer

Once the interface of a collection class has been designed, the implementation involves writing code for the methods specified in the interface.

Question 3

When Python sees the in operator used with a collection, it runs the __contains__ method in the collection's class.

Accepted Answer

The in operator in Python runs the __contains__ method in the collection's class to check if the item is present in the collection.

Question 4

When used with a bag object, the in operator returns an integer value.

Accepted Answer

When used with a bag object, the in operator returns a boolean value (True or False) indicating whether the specified item is present in the bag or not.

Question 5

Software bags can grow as more items are added, or they can shrink as items are removed.

Accepted Answer

Software bags, also known as data structures like linked lists or arrays, are designed to dynamically change in size as items are added or removed. This is one of the key benefits of using these types of structures for storing and manipulating data.

Question 6

The logical size of an array-based bag will always be the same as the array's capacity.

Accepted Answer

The logical size of an array-based bag refers to the number of elements actually stored in the array at any given time, which can be less than or equal to the array's capacity. The capacity is the maximum number of elements the array can hold.

Question 7

A precondition is a statement of what must be true for a method to perform its actions correctly.

Accepted Answer

A precondition is a statement that specifies the required state of the system (inputs or environment) at the start of a method's execution. It defines what must be true for the method to work correctly. If the precondition is not met, the method might not produce the expected results or it might fail altogether.

Question 8

When the LinkedBag structure is not empty, self.items refers to the last node in the linked structure.

Accepted Answer

When the LinkedBag structure is not empty, self.items should refer to the first node in the linked structure, which is the head of the linked list. The head is the starting point of the linked list and holds the first item in the bag.

Question 9

Whenever you need to use the logical size of the bag within a class definition, run len(self) instead of referring directly to the instance variable self.size .

Accepted Answer

Running len(self) retrieves the logical size of the bag, which accounts for any internal changes to the data structure, such as additions or removals. Referring directly to the instance variable self.size may not accurately reflect the current logical size of the bag.

Question 10

Each time you run Python's document function to obtain information about a module, data type, method, or function, you are accessing documentation about that resource's interface.

Accepted Answer

The answer of Each time you run Python's document function...

Question 11

The clear method empties a bag.

Accepted Answer

The sentence states that the "clear method empties a bag", indicating that it is true.

Question 12

The statement in the ArrayBag constructor to copy an item from a source collection to a new ArrayBag object is self.init(item) .

Accepted Answer

The statement in the ArrayBag constructor to copy an item from a source collection to a new ArrayBag object is actually item[i] = self._items[i] and not self.init(item).

Question 13

A bag is a type of ordered collection.

Accepted Answer

A bag is a type of unordered collection where duplicate items are allowed. However, it is not necessarily ordered.

Question 14

When defining the Bag class, the __init__ operation is the constructor for the class.

Accepted Answer

The __init__ operation is indeed the constructor for the Bag class. It is called when a new object of the Bag class is created and allows for initialization of attributes and other necessary setup.

Question 15

An interface's documentation gives you enough information to know how to use or call a method and what to expect it to accomplish and return.

Accepted Answer

The purpose of interface documentation is to provide clear and concise information about the methods that can be called and what they do, including any parameters they take and the expected return values.

Question 16

Data that is needed to represent the state of a collection are assigned instance variables in the __help__ method of the class.

Accepted Answer

Instance variables to represent the state of a collection are typically assigned in the constructor method (e.g., `__init__` in Python) of the class, not in a `__help__` method.

Question 17

You should always try to hide the implementing data structures behind a wall of method calls on the object being implemented.

Accepted Answer

Encapsulating the implementation details of data structures behind a wall of method calls is a fundamental principle of object-oriented programming to ensure better maintainability, flexibility, and security of the code.

Question 18

A docstring is a string enclosed in double quotes that will be displayed when Python's help function is run on a resource.

Accepted Answer

A docstring can be enclosed in triple single quotes (''' ''') or triple double quotes (""" """) and is used for documentation, but it's not limited to being displayed only when Python's help function is run; it can also be accessed through the `.__doc__` attribute of the object.

Question 19

When Python sees a for loop on an iterable object, it runs that object's __add__ method.

Accepted Answer

When Python sees a for loop on an iterable object, it runs that object's __iter__ method, not the __add__ method.

Question 20

The __iter__ method uses a yield statement to send each item to the calling for loop.

Accepted Answer

The __iter__ method in a class is used to define an iterator. It should return an iterator object. The iterator object should have a __next__ method which returns the next value in the iteration. The yield statement can be used inside the __next__ method to send each item to the calling for loop.

Quiz 5: Interfaces, Implementations, and Polymorphism