Python Class Properties and Methods

Python tutorial · PySpark.in

What Are Class Properties?

Class properties (also called attributes) are variables that belong either to:

1. Instance Properties (Instance Variables)

Unique for each object
Stored inside the object
Accessed using self

2. Class Properties (Class Variables)

Shared by all objects of the class
Stored inside the class

Example: Class & Instance Properties

```

class Student:
# Class property
school_name = "D.A.V"
def __init__(self, name, roll):
# Instance properties
self.name = name
self.roll = roll
# Creating objects
s1 = Student("Megha", 101)
s2 = Student("Ravi", 102)
# Accessing instance and class properties
print(s1.name)
print(s2.roll)
print(Student.school_name)

```

Explanation

`school_name` → (Class Property)

Shared by all students
Access using:
- Student.school_name (recommended)
- s1.school_name (works, but not preferred)

`name`, `roll` → Instance Property

Different for every student
Access using:
- object.property

Summary of Property Access

Type	What It Represents	Access Using
Instance Property	Data unique to each object	`object.property`
Class Property	Shared data for all objects	`ClassName.property`

What Are Class Methods?

Methods are functions written inside a class to define behavior.
Python has three types of methods:

Method Type	Description	Uses	Decorator
Instance Method	Works with object data	Access & modify instance variables	—
Class Method	Works with class data	Modify class variables	`@classmethod`
Static Method	Independent utility function	Helper logic with no dependency	`@staticmethod`

Example: Instance, Class, and Static Method

class Student:
 school_name = "Delhi University" # Class property
 def __init__(self, name, roll):
 self.name = name # Instance property
 self.roll = roll
 # Instance method
 def show(self):
 print(f"Name: {self.name}, Roll: {self.roll}")
 # Class method
 @classmethod
 def change_school(cls, new_name):
 cls.school_name = new_name
 # Static method
 @staticmethod
 def info():
 print("This is the Student class for managing student data.")
# Creating objects
s1 = Student("Megha", 101)
s2 = Student("Ravi", 102)
# Calling instance method
s1.show()
# Calling class method
Student.change_school("D.A.V")
# Accessing updated class property
print(Student.school_name)
# Calling static method
Student.info()

▶ Output will appear here.

Explanation of Method Types

Instance Method — `show()`

Works with object data
First parameter → self
Called using: object.method()

Class Method — `change_school()`

Works with the class, not the object
First parameter → cls
Can modify class variables
Called using: ClassName.method()

Static Method — `info()`

Does NOT use self or cls
Helper/utility function inside the class
Called using: ClassName.method()