OOP Concepts Quiz

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Questions and Answers

What is the primary purpose of overriding the magic method eq in a class?

To create a new instance of the class

To store data that is unique to an object

To print the class variable when an object is printed

To enable meaningful comparisons between objects (correct)

Which statement accurately describes class variables?

They are unique to each instance of the class.

They are shared among all instances of the class. (correct)

They are defined inside instance methods.

They can only be accessed through an instance of the class.

How can instance variables be accessed within a class?

Through the class name directly

Using the self keyword (correct)

Only after calling the __init__ method

By referencing the class constructor

If a class does not override the str method, what will typically be output when an object is printed?

The memory address of the object Signup and view all the answers

What best describes instance variables in a class?

They store data that may differ from one instance to another. Signup and view all the answers

What does encapsulation primarily focus on in object-oriented programming?

Controlling access to an object's data Signup and view all the answers

How does inheritance promote code reuse in object-oriented programming?

By allowing a class to inherit attributes and methods from another class Signup and view all the answers

Which statement describes composition in object-oriented programming?

It combines objects of other classes to create a main class. Signup and view all the answers

What distinguishes polymorphism from other object-oriented concepts?

It permits multiple classes to implement the same method uniquely. Signup and view all the answers

What is not a consequence of using inheritance in object-oriented programming?

Flexible system design Signup and view all the answers

In the context of abstraction, which of the following is true?

It hides unnecessary details and shows only relevant functionalities. Signup and view all the answers

What does the 'has a' relationship in composition imply?

One class contains objects of another class. Signup and view all the answers

Which of the following statements represents a distinction between composition and inheritance?

Composition leads to less modification complexity compared to inheritance. Signup and view all the answers

What is the primary purpose of an instance variable in a class?

To store unique values for each instance of the class Signup and view all the answers

How does a class method differ from an instance method?

Class methods are bound to the class, while instance methods are bound to an instance Signup and view all the answers

What will happen when the line 'Person.species = "Homo sapiens sapiens"' is executed?

The species variable for all instances will change to "Homo sapiens sapiens" Signup and view all the answers

What should be the first parameter of a class method?

cls Signup and view all the answers

If the class variable 'wheels' is changed using the class method 'change_wheels', what will be the output of 'car1.describe()' after this change?

This is a red Toyota with the new wheel count. Signup and view all the answers

Which of the following is a valid statement about instance methods and instance variables?

Instance methods can only access other instance variables from the same instance. Signup and view all the answers

What will be the output when 'print(person1.name)' is executed after 'person1.name = "Alicia"'?

Alicia Signup and view all the answers

Which of the following best describes a class variable?

A value shared by all instances of the class Signup and view all the answers

What is the primary purpose of polymorphism in object-oriented programming?

To allow different subclasses to override a method from a superclass Signup and view all the answers

Which method is called when the print() function is used on an object?

str Signup and view all the answers

What will happen if neither str nor repr are defined in a class?

The object's memory address will be printed Signup and view all the answers

When both str and repr methods are defined in a class, which one takes precedence during print operations?

str Signup and view all the answers

What does the eq method determine in a class?

How objects are compared for equality Signup and view all the answers

If a class defines only the repr method but not str, what will print(p) return?

The output from repr Signup and view all the answers

Which of the following is an example of a magic method?

init() Signup and view all the answers

What is the term used for special methods that start and end with double underscores?

Magic methods Signup and view all the answers

What will the output of 'print(even_squares)' be given the definition of even_squares?

[0, 4, 16, 36, 64] Signup and view all the answers

Which of the following correctly describes lambda functions?

They are limited to one line of code. Signup and view all the answers

Given the lambda expression 'add = lambda a, b: a + b', what will 'add(6, 4)' return?

10 Signup and view all the answers

What distinguishes the sorted() function from the sort() method?

sorted() returns a new sorted list. Signup and view all the answers

What is the primary purpose of the map() function in Python?

To apply a function to every item in an iterable. Signup and view all the answers

In the given examples, how does 'filter(lambda x: x % 2 == 0, numbers)' process the numbers list?

It removes all odd numbers from the list. Signup and view all the answers

What would be the outcome of the line 'letters = [word[0] for word in sentence.split()]' given the sentence 'The quick brown fox'?

['T', 'q', 'b', 'f'] Signup and view all the answers

Which of the following statements about hash functions is NOT true?

They always produce a random output. Signup and view all the answers

Study Notes

Encapsulation vs. Abstraction

Encapsulation hides an object's internal data and controls access through methods.
Abstraction hides complexity, revealing only necessary parts for interaction.

Inheritance

Allows a class to inherit attributes and methods from another class, promoting code reuse.
Creates class hierarchies; subclasses inherit and expand superclass behaviors.
Establishes an "is a" relationship (e.g., Dog is an Animal).

Composition

A class is built using objects from other classes.
Provides a modular design, enabling classes to reuse functionality without inheritance.
Establishes a "has a" relationship (e.g., Car has an Engine).

Inheritance vs. Composition

Inheritance is less flexible because subclasses inherit all superclass characteristics, potentially creating dependencies.
Composition is more flexible, allowing classes to be built from independent parts, enabling easier modification.

Polymorphism

Objects of different classes can be treated as objects of a common superclass.
A method operates differently based on the calling object.
Involves defining methods with the same name but different parameters or implementations within a class.

Magic Methods

Special methods allowing customization of how objects interact with built-in operations and functions.
Automatically called by Python during specific operations.
Examples: __str__, __repr__, __eq__

`str` Magic Method

Called by str() and print().
Returns a human-readable string representation of an object.

`repr` Magic Method

Called by repr().
Returns a more formal string representation, suitable for debugging or logging.

`eq` Magic Method

Called by ==.
Defines how two objects are compared for equality.

Class vs. Instance Variables

Class Variables: defined within a class but outside any instance methods; shared by all instances; typically store data common to all instances.
Instance Variables: defined within the __init__ method or any instance method; unique to each instance; store data specific to each object.

Class Methods

Bound to the class, not an instance.
Take the class as the first argument (cls).
Modify class state for all instances or provide utility functions for the class.
Decorated with @classmethod.

List Comprehensions

Provide a concise syntax for creating new lists based on existing lists.
Syntax: [expression for item in iterable (if condition)]

Lambda Anonymous Functions

Syntax: lambda arguments: expression
Define concise, nameless functions for immediate use.
Commonly used within other functions like map(), filter(), and sorted().

Hash Functions

Map data into a fixed-size value, crucial for data structures like dictionaries and sets.
Properties:
- Deterministic: Produce the same output for the same input.
- Efficient: Quickly calculate the hash value.
- Relatively uniform: Distribute input values evenly within the hash range.

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Description

Test your knowledge on key Object-Oriented Programming concepts such as encapsulation, abstraction, inheritance, composition, and polymorphism. This quiz will help you understand how these principles facilitate modular design and code reuse in software development.