Question 1

Consider the following class Time __init__ method: def __init__(self, hour=0, minute=0, second=0):
"""Initialize each attribute."""
Self.hour = hour # 0-23
Self.minute = minute # 0-59
Self.second = second # 0-59
Which of the following statements a), b) or c) is false?
A) Class Time's __init__ method specifies hour, minute and second parameters, each with a default argument of 0.
B) The self parameter is a reference to the Time object being initialized.
C) The statements containing self.hour, self.minute and self.second appear to create hour, minute and second attributes for the new Time object (self). However, these statements may actually call methods that implement the class's hour, minute and second properties.
D) All of the above statements are true.

Accepted Answer

A) The __init__ method does indeed specify hour, minute and second parameters, each with a default argument of 0.
B) The self parameter is a reference to the Time object being initialized. This is true and necessary for accessing and setting the object's attributes.
C) The statements containing self.hour, self.minute and self.second indeed create hour, minute and second attributes for the new Time object (self). There is no indication that these statements are calling methods that implement the class's hour, minute and second properties.
Therefore, all of the statements are true.

Question 2

The ________ special method is called implicitly when you convert an object to a string with the built-in function xe "built-in function:str"xe "str built-in function"str, such as when you print an object or call xe "built-in function:str"xe "str built-in function"str explicitly.
A) __repr__
B) __string__
C) __str__
D) None of the above

Accepted Answer

The __str__ method is called implicitly when converting an object to a string with the built-in function str, making it the best choice for this scenario. The __repr__ method is called when the object needs to be represented in a specific way for debugging purposes. The __string__ method does not exist in Python.

Question 3

Which of the following statements a), b) or c) is false?
A) Each property defines a getter method which gets (that is, returns) a data attribute's value and can optionally define a setter method which sets a data attribute's value.
B) The @property decorator precedes a property's xe "getter method:decorator"getter method, which receives only a self parameter.
C) Behind the scenes, a decorator adds code to the decorated function to enable the function to work with data attribute syntax.
D) All of the above statements are true.

Accepted Answer

All the statements provided are true regarding the use of the @property decorator in Python. Statement A correctly describes the functionality of getter and setter methods in properties. Statement B accurately explains the use of the @property decorator before a getter method, which indeed only receives a self parameter. Statement C correctly describes the role of a decorator in modifying or enhancing functions or methods without changing their code directly.

Question 4

Which of the following statements about a class's utility methods is false?
A) They serve as part of a class's interface.
B) They are used inside the class.
C) They should be named with a single leading underscore.
D) In other object-oriented languages like C++, Java and C#, utility methods typically are implemented as private methods.

Accepted Answer

The answer of Which of the following statements about a...

Question 5

Which of the following statements a), b) or c) is false?
A) It may seem that providing properties with both setters and getters has no benefit over accessing the data attributes directly, but there are subtle differences.
B) A getter seems to allow clients to read the data at will, but the getter can control the formatting of the data.
C) A setter can scrutinize attempts to modify the value of a data attribute to prevent the data from being set to an invalid value.
D) All of the above statements are true.

Accepted Answer

All of the statements A, B, and C are true. Providing properties with both setters and getters has benefits such as encapsulation, validation, and abstraction. A getter can format the data before returning it to the client, while a setter can scrutinize attempts to modify the value and set the value to a valid value.

Question 6

Which of the following statements a), b) or c) is false?
A) Base classes tend to be "more specific" and subclasses "more general."
B) Because every subclass object is an object of its base class, and one base class can have many subclasses, the set of objects represented by a base class is often larger than the set of objects represented by any of its subclasses.
C) The base class Vehicle represents all vehicles, including cars, trucks, boats, bicycles and so on. Subclass Car represents a smaller, more specific subset of vehicles.
D) All of the above statements are true.

Accepted Answer

Explanation: The statement in A is false because it incorrectly describes the relationship between base classes and subclasses. In object-oriented programming, base classes are more general, and subclasses are more specific. Subclasses inherit from base classes and can add or override functionality, making them more specific to a certain type of object.

Question 7

Which of the following statements a), b) or c) is false?
A) A base class exists in a hierarchical relationship with its subclasses.
B) With single inheritance, a class is derived from one base class. With multiple inheritance, a subclass inherits from two or more base classes.
C) One reason to avoid multiple inheritance is the "diamond problem in Python multiple inheritance."
D) All of the above statements are true.

Accepted Answer

All the statements provided are true. Statement A correctly describes the hierarchical relationship between a base class and its subclasses. Statement B accurately explains the difference between single and multiple inheritance. Statement C correctly identifies the "diamond problem" as a reason to be cautious of multiple inheritance, specifically mentioning Python as a context where this issue is relevant.

Question 8

Which of the following statements is false?
A) Sometimes, an attribute should be shared by all objects of a class. A class attribute (also called a class variable) represents class-wide information-it belongs to the class, not to a specific object of that class.
B) You define a class attribute by assigning a value to it inside the class's definition, but not inside any of the class's methods or properties (in which case, they'd be local variables).
C) Class attributes are typically accessed through any object of the class.
D) Class attributes exist as soon as you import their class's definition.

Accepted Answer

Class attributes are accessed using the class name rather than through a specific object to avoid ambiguity and to make it clear that the attribute is class-wide, not instance-specific. Accessing them through any object of the class, while possible, is not the typical or recommended practice.

Question 9

Which of the following statements is false?
A) Python provides two built-in functions-issubclass and isinstance-for testing "is a" relationships.
B) Function issubclass determines whether one class inherits from another.
C) Function isinstance determines whether an object has an "is a" relationship with a specific type.
D) If SalariedCommissionEmployee inherits from CommissionEmployee, and if object s is a SalariedCommissionEmployee, then the following snippet results are correct:
In [19]: isinstance(s, CommissionEmployee)
Out[19]: False
In [20]: isinstance(s, SalariedCommissionEmployee)
Out[20]: True

Accepted Answer

The snippet in option D is incorrect because if SalariedCommissionEmployee inherits from CommissionEmployee, then any instance of SalariedCommissionEmployee is also an instance of CommissionEmployee. Therefore, the output of isinstance(s, CommissionEmployee) should be True.

Question 10

Consider the following code from our class Time: @property
Def hour(self):
"""Return the hour."""
Return self._hour
@hour.setter
Def hour(self, hour):
"""Set the hour."""
If not (0 <= hour < 24):
Raise ValueError(f'Hour ({hour}) must be 0-23')
Self._hour = hour
A) This code defines a read-write property named hour that manipulates a data attribute named _hour.
B) The xe "naming convention:single leading underscore"xe "single leading underscore naming convention"single-leading-underscore (_) naming convention indicates that client code can safely access _hour directly.
C) Properties look like data attributes to programmers working with objects. Properties are implemented as methods.
D) All of the above statements are true.

Accepted Answer

The answer of Consider the following code from our class...

Question 11

Which of the following statements a), b) or c) is false?
A) A class can also support setting its attribute values individually via its properties. Assuming hour is a property of wake_up's class, the following statement changes an hour property value to 6:
Wake_up.hour = 6
B) Though the statement snippet in Part (a) appears to simply assign a value to a data attribute, it's actually a call to an hour method that takes 6 as an argument.
C) The hour method mentioned in Part (b) can validate the value, then assign it to a corresponding data attribute (which we might name _hour, for example).
D) Each of the above statements is true.

Accepted Answer

Each statement accurately describes how properties work in object-oriented programming. Properties allow for the encapsulation of data, enabling both the validation of data before it's assigned and the abstraction of method calls as attribute assignments.

Question 12

A read-only property has ________.
A) only a setter
B) only a getter
C) a setter and a getter
D) neither a setter nor a getter

Accepted Answer

A read-only property only has a getter, allowing clients to retrieve the value but not modify it.

Question 13

Consider the following code which would set the hour of a Time object to an invalid value. wake_up._hour = 100
Which of the following statements is false?
A) Rather than _hour, we can name the attribute __hour with two leading underscores. This convention indicates that __hour is "private" and should not be accessible to the class's xe "client of a class"clients.
B) To help prevent clients from accessing "private" attributes, Python renames them by preceding the attribute name with _ClassName, as in _Time__hour. This is called xe "name mangling"name mangling.
C) If you try to assign to __hour, as in
Wake_up.__hour = 100
Python raises a ValueError, indicating that the class does not have an __hour attribute.
D) IPython does not show attributes with one or two leading underscores when you try to auto-complete an expression like
Wake_up.
By pressing Tab. Only attributes that are part of the wake_up object's "public" interface are displayed in the IPython auto-completion list.

Accepted Answer

Option C is false because Python does not raise a ValueError when assigning to a "private" attribute with two leading underscores. Instead, it performs name mangling and creates a new attribute with a different name. The correct way to access this attribute is to use the mangled name, as in wake_up._Time__hour = 100. Option A, B, and D are all true statements.

Question 14

Properties are implemented as ________, so they may contain additional logic, such as specifying the format in which to return a data attribute's value or validating a new value before using it to modify a data attribute.
A) functions
B) suites
C) classes
D) methods

Accepted Answer

Properties in programming, particularly in object-oriented languages like Python, are implemented as methods. These methods can include additional logic for getting, setting, or deleting an attribute, allowing for validation or formatting of data.

Question 15

The following code and traceback shows that our class Time's hour property xe "validate data"validates the values you assign to it: In [10]: wake_up.hour = 100 --------------------------------------------------------------------- ValueError Traceback (most recent call last) in () ----> 1 wake_up.hour = 100 ~/Documents/examples/ch10/timewithproperties.py in hour(self, hour) 20 """Set the hour.""" 21 if not (0 <= hour < 24): ---> 22 raise ValueError(f'Hour ({hour}) must be 0-23') 23 24 self._hour = hour ValueError: Hour (100) must be 0-23 Which of the following statements a), b) or c) is false? A) The code attempts to set the hour property to an invalid value. B) The code checks that the hour property is in the range 0 through 24. C) The value 100 is out of range so the code raises a ValueError. D) All of the above statements are true.

Accepted Answer

The code checks that the hour property is in the range 0 through 23, not 0 through 24, as indicated by the condition in the code snippet `(0 <= hour < 24)`.

Question 16

Which of the following statements a), b) or c) is false?
A) When you design a class, carefully consider the class's interface before making that class available to other programmers.
B) Unfortunately, existing code will break if you update the class's implementation details-that is, the internal data representation or how its method bodies are implemented.
C) If Python programmers follow convention and do not access attributes that begin with leading underscores, then class designers can evolve class implementation details without breaking client code.
D) All of the above statements are true.

Accepted Answer

While it is important to carefully consider a class's interface and it is true that Python programmers can evolve class implementation details without breaking client code by following conventions, it is not necessarily true that existing code will break if the class's implementation details are updated. Effective use of encapsulation can allow for changes to be made in the internal workings of a class without affecting the external interface. Therefore, statement B is false.

Question 17

Class Time's properties and methods define the class's ________ interface, that is, the properties and methods programmers should use to interact with objects of the class.
A) public
B) private
C) protected
D) None of the above

Accepted Answer

The public interface of a class defines the properties and methods that should be used by programmers to interact with objects of the class. Private properties and methods are only accessible within the class itself, and protected properties and methods are only accessible within the class and its subclasses. None of the above is not a valid answer in this context.

Question 18

Which of the following statements a), b) or c) is false?
A) With inheritance, every object of a subclass also may be treated as an object of that subclass's base class.
B) We can take advantage of this xe ""derived-class-object-is-a-base-class-object" relationship[derived class object is a base class object relationship]""subclass-object-is-a-base-class-object" relationship to place objects related through inheritance into a xe "list of base-class objects"list, then iterate through the list and treat each element as a base-class object.
C) The following code places CommissionEmployee and SalariedCommissionEmployee objects (c and s) in a list, then for each element displays its string representation and earnings-this is an example of xe "polymorphism"polymorphism:
In [21]: employees = [c, s]
In [22]: for employee in employees:
)..: print(employee)
)..: print(f'{employee.earnings():,.2f}
')
)..:
CommissionEmployee: Sue Jones
Social security number: 333-33-3333
Gross sales: 20000.00
Commission rate: 0.10
2,000.00
SalariedCommissionEmployee: Bob Lewis
Social security number: 444-44-4444
Gross sales: 10000.00
Commission rate: 0.05
Base salary: 1000.00
1,500.00
D) All of the above statements are true.

Accepted Answer

All the statements provided are true and accurately describe concepts related to inheritance, polymorphism, and object-oriented programming.

Question 19

Which of the following statements is false?
A) Often, an object of one class is an object of another class as well.
B) A CarLoan is a Loan as are HomeImprovementLoans and MortgageLoans. Class CarLoan can be said to inherit from class Loan.
C) In the context of Part (b), class CarLoan is a base class, and class Loan is a subclass.
D) In the context of Part (b) a CarLoan is a specific type of Loan, but it's incorrect to claim that every Loan is a CarLoan-the Loan could be any type of loan.

Accepted Answer

In the context of Part (b), class CarLoan is a subclass, and class Loan is the base class.

Question 20

Which of the following statements a), b) or c) is false?
A) When you pass an object to built-in function xe "built-in function:repr"xe "repr built-in function"repr-which happens implicitly when you evaluate a variable in an IPython session-the corresponding class's __repr__ special method is called to get the "official" string representation of the object.
B) Typically the string returned by __repr__ looks like a constructor expression that creates and initializes the object, such as:
'Time(hour=6, minute=30, second=0)'
C) Python has a built-in function eval that could receive the string shown in Part (b) as an argument and use it to create and initialize a Time object containing values specified in the string.
D) All of the above statements are true.

Accepted Answer

All of the statements (a), (b), and (c) are true.

Quiz 10: Object-Oriented Programming

Consider the following class Time init method: def init(self, hour=0, minute=0, second=0) : """Initialize each attribute.""" Self.hour = hour # 0-23 Self.minute = minute # 0-59 Self.second = second # 0-59 Which of the following statements a) , b) or c) is false?

The ________ special method is called implicitly when you convert an object to a string with the built-in function xe "built-in function:str"xe "str built-in function"str, such as when you print an object or call xe "built-in function:str"xe "str built-in function"str explicitly.

Which of the following statements a) , b) or c) is false?

Which of the following statements about a class's utility methods is false?

Which of the following statements a) , b) or c) is false?

Which of the following statements a) , b) or c) is false?

Which of the following statements a) , b) or c) is false?

Which of the following statements is false?

Which of the following statements is false?

Consider the following code from our class Time: @property Def hour(self) : """Return the hour.""" Return self._hour @hour.setter Def hour(self, hour) : """Set the hour.""" If not (0 <= hour < 24) : Raise ValueError(f'Hour ({hour}) must be 0-23') Self._hour = hour

Which of the following statements a) , b) or c) is false?

A read-only property has ________.

Consider the following code which would set the hour of a Time object to an invalid value. wake_up._hour = 100 Which of the following statements is false?

Properties are implemented as ________, so they may contain additional logic, such as specifying the format in which to return a data attribute's value or validating a new value before using it to modify a data attribute.

Which of the following statements a) , b) or c) is false?

Class Time's properties and methods define the class's ________ interface, that is, the properties and methods programmers should use to interact with objects of the class.

Which of the following statements a) , b) or c) is false?

Which of the following statements is false?

Which of the following statements a) , b) or c) is false?

Quiz 10: Object-Oriented Programming

Consider the following class Time __init__ method: def __init__(self, hour=0, minute=0, second=0) : """Initialize each attribute.""" Self.hour = hour # 0-23 Self.minute = minute # 0-59 Self.second = second # 0-59 Which of the following statements a) , b) or c) is false?

The ________ special method is called implicitly when you convert an object to a string with the built-in function xe "built-in function:str"xe "str built-in function"str, such as when you print an object or call xe "built-in function:str"xe "str built-in function"str explicitly.

Which of the following statements a) , b) or c) is false?

Which of the following statements about a class's utility methods is false?

Which of the following statements a) , b) or c) is false?

Which of the following statements a) , b) or c) is false?

Which of the following statements a) , b) or c) is false?

Which of the following statements is false?

Which of the following statements is false?

Consider the following code from our class Time: @property Def hour(self) : """Return the hour.""" Return self._hour @hour.setter Def hour(self, hour) : """Set the hour.""" If not (0 <= hour < 24) : Raise ValueError(f'Hour ({hour}) must be 0-23') Self._hour = hour

Which of the following statements a) , b) or c) is false?

A read-only property has ________.

Consider the following code which would set the hour of a Time object to an invalid value. wake_up._hour = 100 Which of the following statements is false?

Properties are implemented as ________, so they may contain additional logic, such as specifying the format in which to return a data attribute's value or validating a new value before using it to modify a data attribute.

Which of the following statements a) , b) or c) is false?

Class Time's properties and methods define the class's ________ interface, that is, the properties and methods programmers should use to interact with objects of the class.

Which of the following statements a) , b) or c) is false?

Which of the following statements is false?

Which of the following statements a) , b) or c) is false?

Consider the following class Time init method: def init(self, hour=0, minute=0, second=0) : """Initialize each attribute.""" Self.hour = hour # 0-23 Self.minute = minute # 0-59 Self.second = second # 0-59 Which of the following statements a) , b) or c) is false?