Unit 5: Classes and objects; Object oriented programming terminology - Practice Quiz

1 Which keyword is used to create a class in Python?

2 Which statement correctly defines an empty class named Student?

3 Which special method is commonly used to initialize a new object's attributes?

4 Given class Car: pass, which statement creates an instance of Car?

5 What is an instance object?

6 In an instance method, what does the parameter self normally refer to?

7 If student has an attribute named name, how is that attribute accessed?

8 Which statement assigns the value 20 to the age attribute of person?

9 Which built-in function retrieves a named attribute from an object?

10 What does class inheritance allow a child class to do?

11 Which syntax defines Dog as a child class of Animal?

12 In class SavingsAccount(Account):, which class is the parent class?

13 What is method overriding?

14 A parent class and a child class both define display(). Which version is normally called on a child object?

15 Which function is commonly used to call a parent class method from a child class?

16 Which attribute name uses Python's double-underscore convention for data hiding?

17 What is the main purpose of data hiding in a class?

18 What happens to an attribute named __code inside a class named Product?

19 Does Python directly support traditional function overloading by defining several functions with the same name and different parameter lists?

20 Which Python feature can let one function accept different numbers of positional arguments?

21 What is printed by the following code?

class Counter:
    total = 0

    def __init__(self):
        Counter.total += 1

Counter()
Counter()
c = Counter()
print(c.total)

22 Which class definition correctly initializes each Book object with separate title and price attributes?

23 What is the result of the following code?

class Rectangle:
    def __init__(self, width, height=2):
        self.width = width
        self.height = height

    def area(self):
        return self.width * self.height

r = Rectangle(5)
print(r.area())

24 Given the class below, which statement creates a valid instance whose name is 'Asha'?

class Student:
    def __init__(self, name):
        self.name = name

25 What is printed by the following code?

class Box:
    def __init__(self, value):
        self.value = value

b1 = Box(4)
b2 = b1
b2.value = 9
print(b1.value, b2.value)

26 What does the expression p1 is p2 evaluate to?

class Point:
    def __init__(self, x):
        self.x = x

p1 = Point(3)
p2 = Point(3)

27 What is printed by this code?

class Device:
    category = 'electronic'

    def __init__(self, category):
        self.category = category

d = Device('sensor')
print(d.category, Device.category)

28 Which expression safely returns the salary attribute of employee, or 0 if that attribute does not exist?

29 What is printed by the following program?

class Account:
    rate = 5

    def __init__(self):
        self.rate = 7

a = Account()
del a.rate
print(a.rate)

30 What is printed by this code?

class Vehicle:
    wheels = 4

class Bike(Vehicle):
    wheels = 2

class Scooter(Bike):
    pass

print(Scooter.wheels)

31 What is the output of the following code?

class Parent:
    def __init__(self, value):
        self.value = value

class Child(Parent):
    def __init__(self, value):
        super().__init__(value * 2)

c = Child(6)
print(c.value)

32 Given class Manager(Employee, Auditor):, which statement best describes where Python first searches for an inherited method called by a Manager object?

33 What is printed by this code?

class Animal:
    def speak(self):
        return 'sound'

class Dog(Animal):
    def speak(self):
        return 'bark'

a = Animal()
d = Dog()
print(a.speak(), d.speak())

34 What does PremiumBill.total() return?

class Bill:
    def total(self):
        return 100

class PremiumBill(Bill):
    def total(self):
        return super().total() + 20

b = PremiumBill()

35 Which method definition in Child overrides Parent.process while still reusing the parent's result?

class Parent:
    def process(self, value):
        return value * 2

36 What is the most likely result of directly evaluating v.__speed?

class Vehicle:
    def __init__(self):
        self.__speed = 60

v = Vehicle()

37 Which expression accesses the name-mangled value of __balance from the object a?

class Account:
    def __init__(self):
        self.__balance = 500

a = Account()

38 What is printed by this code?

class Base:
    def __init__(self):
        self.__value = 10

class Child(Base):
    def __init__(self):
        super().__init__()
        self.__value = 20

c = Child()
print(c._Base__value, c._Child__value)

39 What happens when this code runs?

class Calculator:
    def add(self, a, b):
        return a + b

    def add(self, a, b, c):
        return a + b + c

calc = Calculator()
print(calc.add(2, 3))

40 Which implementation most directly supports calls such as area(5) for a square and area(5, 3) for a rectangle?

41 What is printed by the following code?

class A:
    def __new__(cls):
        print("new")
        return object()

    def __init__(self):
        print("init")

a = A()
print(type(a).__name__)

42 What happens when this class definition is executed in Python 3?

class C:
    x = 4
    values = [x * i for i in range(3)]

43 What is printed by the following descriptor example?

class D:
    def __get__(self, obj, owner):
        return 10

    def __set__(self, obj, value):
        obj.__dict__["x"] = value * 2

class C:
    x = D()

c = C()
c.x = 3
print(c.__dict__["x"], c.x)

44 What is printed by this code?

class C:
    def __init__(self):
        self.x = 5

    def __getattribute__(self, name):
        if name == "x":
            raise AttributeError(name)
        return object.__getattribute__(self, name)

    def __getattr__(self, name):
        return f"missing:{name}"

print(C().x)

45 What is printed by this cooperative multiple-inheritance example?

class A:
    def f(self):
        return ["A"]

class B(A):
    def f(self):
        return ["B"] + super().f()

class C(A):
    def f(self):
        return ["C"] + super().f()

class D(B, C):
    def f(self):
        return ["D"] + super().f()

print(D().f())

46 Given the following hierarchy, which implementation handles D().ping()?

class A:
    def ping(self):
        return "A"

class B(A):
    pass

class C(A):
    def ping(self):
        return "C"

class D(B, C):
    pass

47 What happens when the final two statements execute?

class Base:
    @classmethod
    def identify(cls):
        return cls.__name__

class Child(Base):
    def identify(self):
        return "instance"

print(Child().identify())
print(Child.identify())

48 What is printed by this code?

class Box:
    def __len__(self):
        return 1

b = Box()
b.__len__ = lambda: 99
print(len(b), b.__len__())

49 What is printed by the following code using double-underscore names?

class A:
    __value = 1

    def get(self):
        return self.__value

class B(A):
    __value = 2

b = B()
print(b.get(), b._B__value)

50 What is printed after directly placing x in the instance dictionary?

class C:
    @property
    def x(self):
        return 7

c = C()
c.__dict__["x"] = 20
print(c.x)

51 What happens when C().f(10) is evaluated?

class C:
    def f(self, x):
        return x

    def f(self, x, y):
        return x + y

52 What is the runtime result of the final call?

from typing import overload

@overload
def convert(x: int) -> str: ...

@overload
def convert(x: str) -> int: ...

def convert(x):
    return x

print(convert(4))

53 What does this singledispatch function print?

from functools import singledispatch

@singledispatch
def describe(value):
    return "object"

@describe.register
def _(value: int):
    return "integer"

print(describe(True))

54 What is printed when the metaclass modifies each new class namespace?

class Meta(type):
    def __new__(mcls, name, bases, namespace):
        namespace["x"] = namespace.get("x", 0) + 1
        return super().__new__(mcls, name, bases, namespace)

class A(metaclass=Meta):
    x = 4

class B(A):
    pass

print(A.x, B.x)

55 What happens in this descriptor example?

class Descriptor:
    def __set_name__(self, owner, name):
        self.name = name

    def __get__(self, obj, owner):
        return self.name

class C:
    pass

C.x = Descriptor()
print(C().x)

56 What is printed when an instance attribute has the same name as this descriptor?

class Descriptor:
    def __get__(self, obj, owner):
        return 10

class C:
    x = Descriptor()

c = C()
c.__dict__["x"] = 30
print(c.x)

57 What list is printed after cooperative initialization?

class A:
    def __init__(self, log):
        log.append("A")

class B(A):
    def __init__(self, log):
        log.append("B")
        super().__init__(log)

class C(A):
    def __init__(self, log):
        log.append("C")
        super().__init__(log)

class D(B, C):
    pass

log = []
D(log)
print(log)

58 What is printed when a subclass defines a method with the same private spelling?

class A:
    def __run(self):
        return "A"

    def execute(self):
        return self.__run()

class B(A):
    def __run(self):
        return "B"

print(B().execute())

59 What is printed after the augmented assignment and the ordinary assignment?

class C:
    items = []

a = C()
b = C()
a.items += [1]
b.items = b.items + [2]
print(C.items, a.items, b.items)

60 What happens when the final expression is evaluated?

class Base:
    def value(self):
        return 5

class Child(Base):
    @property
    def value(self):
        return 8

result = Child().value()