pythonintermediate

Python Object-Oriented Programming

Classes, inheritance, polymorphism, magic methods and properties

7 questions

By EZ4Code TeamLast updated: 2026-08-01

1. Which of the following descriptions of Python's init method is correct?

It is the class constructor, automatically called when creating an instance

It is the class destructor, called when destroying an instance

It must return a value

It cannot take parameters

Explanation: __init__ is the initialization method (constructor), automatically called when instantiating an object, used to initialize instance attributes, and does not need to return a value.

2. Regarding inheritance, what does the following code output? class A: def speak(self): return 'A' class B(A): def speak(self): return 'B' b = B() print(b.speak())

class A:
    def speak(self):
        return 'A'

class B(A):
    def speak(self):
        return 'B'

b = B()
print(b.speak())

Error

Explanation: Subclass B overrides the speak method of parent class A. The Method Resolution Order (MRO) prioritizes the subclass method, so it outputs 'B'.

3. What is the main purpose of using super()?

To call the parent class method, avoiding hardcoding the parent class name

To create a new object

To access private attributes

To delete an instance

Explanation: super() is used to call parent class methods, follows the MRO in multiple inheritance, and avoids hardcoding parent class names for easier maintenance.

4. Which of the following is the correct way to define a class method (classmethod)?

class MyClass:
    @classmethod
    def foo(cls):
        pass

Use the @classmethod decorator, with cls as the first parameter

Use the @staticmethod decorator, with self as the first parameter

Use the @property decorator

No decorator needed

Explanation: Class methods use the @classmethod decorator, with the first parameter being the class itself (conventionally cls), which can access and modify class-level state.

5. What does the @property decorator do?

Converts a method into read-only property access

Declares a static variable

Declares an abstract method

Declares a private method

Explanation: @property wraps a method as a property, accessible via obj.name, often combined with @name.setter for controllable read/write access.

6. What is the difference between the magic methods str and repr?

__str__ is user-readable, __repr__ is developer-oriented and strives to be unambiguous

They are completely identical

__repr__ is user-oriented, __str__ is developer-oriented

Only __str__ exists

Explanation: __str__ returns a user-friendly string (used by print); __repr__ returns the official string (used for debugging, repr()), and should ideally be able to reproduce the object.

7. Regarding polymorphism, which statement is correct?

Objects of different classes can achieve polymorphism by implementing methods with the same name, without needing to inherit from the same parent class

Polymorphism must rely on a strong type system

Python does not support polymorphism

Polymorphism can only be achieved through abstract base classes

Explanation: Python is a dynamic language; polymorphism is based on duck typing: as long as an object implements the required methods, it doesn't need to inherit from the same parent class.

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