Below is a clear, complete, and exam-oriented explanation of Accessing Attributes, Editing Class Attributes, and Built-in Class Attributes in Python OOP — perfect for BCA/MCA/B.Tech students.

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⭐ 1. Accessing Attributes in Python

Attributes are variables that belong to a class or to an object.

There are two types:

• Instance attributes → belong to each object
• Class attributes → shared among all objects

To access attributes, we use the dot operator (.).

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✔ Accessing Instance Attributes

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

s1 = Student("Amit", 101)

print(s1.name)   # Access attribute
print(s1.roll)

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✔ Accessing Class Attributes

class Student:
    college = "XYZ University"    # class attribute

s1 = Student("Amit", 101)
print(s1.college)                 # via object
print(Student.college)            # via class

✔ Both ways are allowed
❗ Best practice → access class attributes using class name

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⭐ 2. Editing Class Attributes

Class attributes can be modified using:

✔ A. Class name (Recommended)

class Student:
    college = "XYZ University"

Student.college = "ABC College"   # modify class attribute

s1 = Student("Amit", 101)
s2 = Student("Rita", 102)

print(s1.college)  # ABC College
print(s2.college)  # ABC College

👉 All objects see the updated value because class attributes are shared.

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✔ B. Editing via object (Not recommended)

This does not change the class attribute.
It creates a new instance attribute.

s1.college = "New College"  
print(s1.college)        # New College
print(Student.college)   # ABC College (unchanged)

✔ Only s1 is affected.
✔ Confirms class attribute is different from instance attribute.

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⭐ 3. Editing Instance Attributes

Instance attributes are edited per object.

s1.name = "Arjun"
print(s1.name)

✔ Only that object gets updated.

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⭐ 4. How Python Looks for an Attribute (Resolution Order)

When accessing s1.college:

1. Python checks instance attributes
2. If not found → checks class attributes
3. If still not found → checks parent classes (inheritance)

This is known as Attribute Resolution Order (MRO).

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⭐ 5. Built-in Class Attributes

Python classes come with several built-in attributes that give metadata about the class.

Here are the most important ones for exams:

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✔ 1. __dict__

Stores all attributes of a class or object as a dictionary.

class Student:
    college = "XYZ University"

print(Student.__dict__)

For an object:

s1 = Student()
print(s1.__dict__)

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✔ 2. __doc__

Shows the documentation string of the class.

class Student:
    """This class represents student information."""
    pass

print(Student.__doc__)

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✔ 3. __name__

Holds the class name.

print(Student.__name__)

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✔ 4. __module__

Shows the module where the class is defined.

print(Student.__module__)

If in the same file → output is "__main__".

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✔ 5. __bases__

Shows base classes (important for inheritance).

class A:
    pass

class B(A):
    pass

print(B.__bases__)   # (<class '__main__.A'>,)

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✔ 6. __class__

Used with objects to show which class they belong to.

s1 = Student()
print(s1.__class__)

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⭐ Example Demonstrating All Concepts

class Employee:
    """Employee class"""
    company = "TechCorp"     # class attribute

    def __init__(self, name, salary):
        self.name = name     # instance attribute
        self.salary = salary

# Creating objects
e1 = Employee("Ravi", 50000)

# Accessing attributes
print(e1.name)
print(Employee.company)

# Editing class attribute
Employee.company = "NewCorp"

# Built-in class attributes
print(Employee.__name__)
print(Employee.__doc__)
print(Employee.__dict__)
print(Employee.__module__)
print(Employee.__bases__)

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⭐ Exam-Ready Summary

Accessing Attributes:

• Use the dot operator (object.attribute or class.attribute).
• Instance attributes differ for each object, class attributes are shared.

Editing Class Attributes:

• Use ClassName.attribute = value to update for all objects.
• Editing via object creates a new instance attribute and does not change the class attribute.

Built-in Class Attributes:

• __dict__ → dictionary of class attributes
• __doc__ → class documentation
• __name__ → class name
• __module__ → module name
• __bases__ → base classes

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