Inner Class.md

Inner Class

A class defined in another class is known as inner class. A parent class can have one or more inner class.

First we create a class and then the constructor of the class.

After creating a class, we will create another class within that class, the class inside another class will be called as inner class.

main.py

class Varsity:

	def __init__(self, name, deptNo):
		self.name = name
		self.deptNo = deptNo
		self.cse = self.Cse() # create Cse object as cse

	def display(self):
		print(f"{self.name} has {self.deptNo} departments")


	class Cse:

		def __init__(self):
			self.student = 100
		
		def displayStudentNo(self):
			print(f"displayStudentNo called and print :Cse has {self.student} students")


var = Varsity("Sust", 28)
var.display()

var.cse.displayStudentNo() # call display method of cse class

dept = var.cse # assigning cse object to dept

dept.displayStudentNo()

output:

Sust has 28 departments
displayStudentNo called and print :Cse has 100 students
displayStudentNo called and print :Cse has 100 students

Here:

1. We implement Cse class in the Varsity class as inner class

2. Create a object named 'cse' of Cse class inside the constructor of Varsity class.

3. Then we create a object of Varsity class named 'var' which create 'cse' object of Cse class

4. Then we print display method of var object and displayStudentNo of cse object.

Lets try to understand another code :

main.py

class Varsity:
	name = "sust"

	def __init__(self, name, deptNo):
		self.name = name
		self.deptNo = deptNo
		self.cse = self.Cse() # create Cse object as cse

	def display(self):
		print(f"{self.name} has {self.deptNo} departments")


	class Cse:
		name = "Cse"

		def __init__(self):
			self.student = 100

		@classmethod
		def displayClassName(cls):
			print(f"displayClassName called and print :{cls.name}")
		
		def displayStudentNo(self):
			print(f"displayStudentNo called and print :Cse has {self.student} students")


print(Varsity.name) # called 'name' class variable of Varsity class
print(Varsity.Cse.name) # called 'name' class variable of Cse class

Varsity.Cse.displayClassName() # called 'displayClassName()' class method of Cse class

var = Varsity("Sust", 28) # Create a object of Varsity class
var.display() # class 'display()' instance method of Varsity class

var.cse.displayStudentNo() # called 'displayStudentNo()' instance method of cse object

dept = var.cse # assigning cse object to dept

dept.displayStudentNo() # called 'displayStudentNo()' instance method through dept variable 

For more about inner class follow this link.

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