Advanced OOP - Quiz

Complete the code to create an immutable data class instance representing a coordinate

In a data class, which parameter makes instances immutable after creation?

What is a primary benefit of using __slots__ in a class?

Which built-in is the default metaclass in Python?

A descriptor must implement at least one of which methods?

What does a class decorator receive as its first argument?

What is a typical use case for a mixin class?

When you define __slots__ = ['name'] in a class without __dict__ in slots, what happens?

Which statement about data classes and __slots__ is correct?

What is a key difference between a metaclass and a class decorator?

A data descriptor is one that implements:

Why should most mixin classes avoid defining __init__?

Which is a practical use of a metaclass?

Order the steps to create a data class that validates age using a descriptor.

Drag and drop to reorder, or use the arrows.

Order the steps to apply a class decorator that injects a mixin's methods into a target class.

Drag and drop to reorder, or use the arrows.

What is the output of this code using a data class?

1from dataclasses import dataclass
2
3@dataclass
4class Product:
5    name: str
6    price: float
7
8item = Product("Pen", 1.5)
9print(item == Product("Pen", 1.5))

What is the output when accessing a descriptor-backed attribute?

1class Uppercase:
2    def __get__(self, instance, owner):
3        return instance._name.upper()
4    def __set__(self, instance, value):
5        instance._name = value
6
7class User:
8    name = Uppercase()
9
10u = User()
11u.name = "alice"
12print(u.name)

What will this __slots__-based class print?

1class Slotted:
2    __slots__ = ('value',)
3    def __init__(self, value):
4        self.value = value
5
6s = Slotted(10)
7print(hasattr(s, '__dict__'))

What is printed when using a simple class decorator?

1def tagged(cls):
2    cls.tag = "service"
3    return cls
4
5@tagged
6class Service:
7    pass
8
9print(Service.tag)

What is the output of this metaclass-based registration?

1registry = []
2
3class AutoRegister(type):
4    def __new__(mcls, name, bases, attrs):
5        cls = super().__new__(mcls, name, bases, attrs)
6        if name != 'Base':
7            registry.append(name)
8        return cls
9
10class Base(metaclass=AutoRegister):
11    pass
12
13class Task(Base):
14    pass
15
16print(registry)

Find the bug in this descriptor-based validation code.

Click on the line(s) that contain the bug.

class Positive:

    def __get__(self, instance, owner):

        return instance._value

    def __set__(self, instance, value):

        if value <= 0:

            raise ValueError("must be positive")

        _value = value

class Account:

    balance = Positive()

    def __init__(self, starting):

        self.balance = starting

Find the bug in this __slots__ and mixin combination.

Click on the line(s) that contain the bug.

class LoggingMixin:

    def log(self, msg):

        print(f"LOG: {msg}")

class User(LoggingMixin):

    __slots__ = ('name')

    def __init__(self, name):

        super().__init__()

        self.name = name

Match each concept with the best description.

Click an item on the left, then click its match on the right. Click a matched item to unmatch.

Match each advanced OOP feature with a realistic use case.

Click an item on the left, then click its match on the right. Click a matched item to unmatch.

Complete the data class code so that new ids are generated automatically and total is computed.

Complete the code to define a mixin that uses a descriptor for validated age.

Click the line that prevents adding new attributes dynamically due to __slots__.

Click on the line to select.

class Record:

    __slots__ = ('id', 'name')

    def __init__(self, id, name):

        self.id = id

        self.name = name

r = Record(1, 'item')

# r.extra = 'not allowed'  # would raise AttributeError

Click the line where the metaclass customizes class creation.

Click on the line to select.

class NamingMeta(type):

    def __new__(mcls, name, bases, attrs):

        attrs['created_by_meta'] = True

        return super().__new__(mcls, name, bases, attrs)

class Service(metaclass=NamingMeta):

    pass

print(Service.created_by_meta)