Deck 5: Interfaces, Implementations, and Polymorphism

Question 1

You can use a for loop on any collection.

Answer 1

True

Question 2

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

Answer 2

True

Question 3

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

Answer 3

True

Question 4

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

Question 5

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

Question 6

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

Question 7

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

Question 8

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

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 .

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.

Question 11

The clear method empties a bag.

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) .

Question 13

A bag is a type of ordered collection.

Question 14

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

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.

Question 16

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

Question 17

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

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.

Question 19

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

Question 20

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

Question 21

Which of the following is one of the hallmarks of well-designed software?

A) a random grouping of interfaces to ensure secure code
B) an interface that is tightly coupled to the implementation
C) the clean separation of interfaces from implementations
D) a sophisticated interface with a high learning curve

Question 22

In the Bag class defined in the chapter, what is one of the purposes of the sourceCollection argument in the __init__ method?

A) to create a bag with the contents of another collection
B) to delete the contents of an existing collection
C) to define source code for the method
D) to add data to an existing bag collection

Question 23

In the ArrayBag class, why must the ArrayBag object track its logical size in a separate instance variable?

A) because the physical size is always smaller than the logical size
B) because the initial size of the object can't be changed
C) because the logical size will likely differ from the array's capacity
D) because the array size and the logical size are identical

Question 24

The running times of the operations of ArrayBag and LinkedBag are similar.

Question 25

In the remove method for LinkedBag, if probe points to the node at the head of the linked structure, trailer will point to the tail.

Question 26

What word is best defined as the use of common names for operations on different types of collections?

A) anachronism
B) polymorphism
C) concatenation
D) modularization

Question 27

The design and implementation of a collection class consists of two steps. What is the first step?

A) document the class using docstrings
B) choose an appropriate data structure
C) write the code for the defined methods
D) test the method using sample data

Question 28

What is the name of the method that performs the constructor operation for a class?

A) __eq__
B) __iter__
C) __add__
D) __init__

Question 29

The code for the add method for the ArrayBag class is shown below. What is the missing code?
Def add(self, item):
Self.items[len(self)] = item
< missing code >

A) self.items +=1
B) self = self + 1
C) self.size += 1
D) self.len = self.items

Question 30

In the ArrayBag class, what must the __init__ method do if a source collection is specified?

A) the new instantiation of the bag must be copied to the source collection.
B) the source collection must be initialized with the clear method
C) the data in the source collection must be deleted
D) the data in the source collection must be copied

Question 31

What does Python do when it sees a for loop on an iterable object?

A) executes a do loop
B) runs the __iter__ method
C) runs the clear method
D) executes a return statement

Question 32

Which Python function allows you to obtain information about a module, data type, method, or function?

A) help
B) list
C) doc
D) info

Question 33

The __iter__ method is identical in the ArrayBag and LinkedBag classes.

Question 34

Which of the following is NOT a goal of the barrier that separates an interface from implementation?

A) allows users to quickly glue resources together
B) allows alternative implementations of the same resource
C) changes to a resource's implementations do not disturb user code
D) increases the learning curve for resource's users

Question 35

Class diagrams show the relationships among classes at various levels of detail.

Question 36

Which is true about a bag collection?

A) it is an unordered collection
B) it is a standard collection type in Python
C) bags can contain only numeric objects
D) bags are of a fixed size

Question 37

What is found in the body of the method code that is used to document the method?

A) mutators
B) parameters
C) docstring
D) arguments

Question 38

While desirable, testing is not a critical part of software resource development.

Question 39

The code for the __iter__ method is shown below. What is the missing code?
Def __iter__(self):
< missing code >
While cursor < len(self):
Yield self.items[cursor]
Cursor += 1

A) cursor = 0
B) cursor = 1
C) cursor = self.size
D) cursor = len(self)

Question 40

What is it called when the contents of two bags are combined into a third bag?

A) iteration
B) appending
C) concatenation
D) reduction

Question 41

Why won't some of the ArrayBag methods require changes when implementing the LinkedBag class?

A) because the methods don't use the self variable
B) because the ArrayBag class is based on lists
C) because the LinkedBag object is not iterable
D) because the methods don't directly access the array variable

Question 42

Which of the following methods will require changes between the ArrayBag and the LinkedBag class?

A) isEmpty
B) remove
C) __eq__
D) __len__

Question 43

What testing tool can be used to help ensure that a resource meets its requirements?

A) unittest
B) pytest
C) pyunit
D) unitcheck

Question 44

The following code copies the data from a specified source collection in the LinkedBag __init__ method. What is the missing code? for item in sourceCollection:
< missing code >

A) add(item.self)
B) self.add(item)
C) self.item(add)
D) self.item = source.item

Question 45

What is the last step in the remove function in the ArrayBag class?

A) check the precondition
B) shift items to the right
C) resize the array
D) search for the target item index

Question 46

What method does Python run when it sees the in operator used with a collection?

A) __contains__
B) __iter__
C) __eq__
D) __add__

Question 47

In the ArrayBag class, what function does the __str__ method use to generate a sequence of strings from a bag?

A) count
B) len
C) add
D) map

Question 48

What is one of the pieces of data that must be initialized in the __init__ method in the LinkedBag class?

A) an array
B) a linked structure
C) a physical size
D) a string pointer

Question 49

How can the performance of the in and remove functions be described in the two bag implementations?

A) they take linear time
B) they take constant time
C) the performance is exponential according to the size of the bag
D) the performance is logarithmic according to the size of the bag

Question 50

Which of the following is a visual aid to help catalog resources in your software toolbox?

A) docstring
B) method mapper
C) unit modeler
D) class diagram