Solving a problem by creating objects is on of the most popular approaches in programming. This is called OOP.
This concept focuses on using reusable code, which implements DRY principle
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| oop |
Class : A class is a blueprint for creating objects.
syntax:
Class Emp :
#methods and variables
Object: Object is an instantiation of a class. when class is defined, a template (info) is defined. memory is allocated only after object instantiation.
Objects of a given class can invoke the methods available to it without revealing the implementation details to the user. : Abstraction and Encapsulation
Modelling a problem in OOP's : we identify the following in our program
Noun : class : Emp
Adjective : Attributes : name, age
Verbs : Methods : getsal(), inc()
Class Attributes : An attribute that belongs to the class rather than a particular object.
Class Emp :
company = "google" : [specific to each class]
praveen = Emp() : [object instantiation]
praveen.company
Emp.company = "YouTube" : [changing class attribute]
Instance Attributes : an attribute that belongs to the Instance (object) assuming the class from the previous example :
praveen.name = "praveen"
praveen.salary = "50k" : [adding instance attributes]
***Instance attributes take preference over class attributes during assignment and retrieval.
self parameter: self refers to the instance of the class. Itis automatically passed with a function call from an object.
praveen.getsal() : here self is praveen and equivalent to Emp getal(praveen)
The function getsal is defined as :
Class Emp :
company = "Google"
def getsal(self) :
print("Salary not mentioned")
Static Method : Sometimes we need a function that doesn't use the self parameter. we can define a static method :
@staticmethod : [decorator to mark greet as a static method]
def greet() :
print("hello user")
--init-- () constructor : is a special method wi=hich is first run as soon as the object is created. this method is also known as constructor. it takes self arguement and can also take further arguements.
Class Emp :
def --init-- (self, name) :
self. name = name
def getsal(self) :
....
praveen = Emp ("praveen") : [Object can be instantiated using constructor]
Programs :
1. #oop's concept
class Number:
def sum(self):
return self.a + self.b
num = Number()
num.a = 12
num.b = 34
s = num.sum()
print(s)
# a = 12
# b = 34
# print("The sum of a and b is ", a+b)
'''
PascalCase
EmployeeName -->PascalCase
camelCase
isNumeric, isFloatOrInt -->camelCase
'''
2. #game example
class Remote():
pass
class Player:
def moveRight(self):
pass
def moveLeft(self):
pass
def moveTop(self):
pass
remote1 = Remote()
player1 = Player()
if(remote1.isLeftPressed()):
player1.moveLeft()
3. #Employee example
class Employee:
company = "Google"
salary = 100
praveen= Employee()
rajni = Employee()
praveen.salary = 300
rajni.salary = 400
print(praveen.company)
print(rajni.company)
Employee.company = "YouTube"
print(praveen.company)
print(rajni.company)
print(praveen.salary)
print(rajni.salary)
4. #instance class attribute
class Employee:
company = "Google"
salary = 100
praveen = Employee()
rajni = Employee()
# Creating instance attribute salary for both the objects
# praveen.salary = 300
# rajni.salary = 400
praveen.salary = 45
print(praveen.salary)
print(rajni.salary)
# Below line throws an error as address is not present in instance/class
# print(rajni.address)
5. #Self
class Employee:
company = "Google"
def getSalary(self):
print(f"Salary for this employee working in {self.company} is {self.salary}")
praveen = Employee()
praveen.salary = 100000
praveen.getSalary() # Employee.getSalary(harry)
6. #static method
class Employee:
company = "Google"
def getSalary(self, signature):
print(f"Salary for this employee working in {self.company} is {self.salary}\n{signature}")
@staticmethod
def greet():
print("Good Morning, Sir")
@staticmethod
def time():
print("The time is 9AM in the morning")
praveen = Employee()
praveen.salary = 100000
praveen.getSalary("Thanks!") # Employee.getSalary(harry)
praveen.greet() # Employee.greet()
praveen.time()
7. #constructor
class Employee:
company = "Google"
def __init__(self, name, salary, subunit):
self.name = name
self.salary = salary
self.subunit = subunit
print("Employee is created!")
def getDetails(self):
print(f"The name of the employee is {self.name}")
print(f"The salary of the employee is {self.salary}")
print(f"The subunit of the employee is {self.subunit}")
def getSalary(self, signature):
print(f"Salary for this employee working in {self.company} is {self.salary}\n{signature}")
@staticmethod
def greet():
print("Good Morning, Sir")
@staticmethod
def time():
print("The time is 9AM in the morning")
praveen = Employee("praveen", 100, "YouTube")
# praveen = Employee() --> This throws an error (missing 3 required positional arguments:)
praveen.getDetails()
