Class, object and inheritance in python
- 1. OOPs CONCEPT IN PYTHON SANTOSH VERMA Faculty Development Program: Python Programming JK Lakshmipat University, Jaipur (3-7, June 2019)
- 2. Important Note Please remember that Python completely works on indentation. Use the tab key to provide indentation to your code.
- 3. Classes and Objects Classes Just like every other Object Oriented Programming language Python supports classes. Let’s look at some points on Python classes. Classes are created by keyword class. Attributes are the variables that belong to class. Attributes are always public and can be accessed using dot (.) operator. Eg.: Myclass.Myattribute
- 4. # A simple example class class Test: # A sample method def fun(self): print("Hello") # Driver code obj = Test() obj.fun() Output: Hello
- 5. The self Class methods must have an extra first parameter in method definition. do not give a value for this parameter when we call the method, Python provides it. If we have a method which takes no arguments, then we still have to one argument – the self. See fun() in above simple example. This is similar to this pointer in C++ and this reference in Java. When we call a method of this object as myobject.method(arg1, arg2), is automatically converted by Python into MyClass.method(myobject, arg2) – this is all the special self is about.
- 6. # creates a class named MyClass class MyClass: # assign the values to the MyClass attributes number = 0 name = "noname" def Main(): # Creating an object of the MyClass.Here, 'me' is the object me = MyClass() # Accessing the attributes of MyClass, using the dot(.) operator me.number = 310 me.name = "Santosh" # str is an build-in function that, creates an string print(me.name + " " + str(me.number)) # telling python that there is main in the program. if __name__=='__main__': Main() Output: Santosh 310
- 7. The __init__ method The __init__ method is similar to constructors in C++ and Java. It is run as soon as an object of a class is instantiated. The method is useful to do any initialization you want to do with your object. class Person: # init method or constructor def __init__(self, name): self.name = name # Sample Method def say_hi(self): print('Hello, my name is', self.name) p = Person(‘Santosh') p.say_hi()
- 8. Methods Method is a bunch of code that is intended to perform a particular task in your Python’s code. Function that belongs to a class is called an Method. All methods require ‘self’ first parameter. If you have coded in other OOP language you can think of ‘self’ as the ‘this’ keyword which is used for the current object. It unhides the current instance variable. ’self’ mostly work like ‘this’. ‘def’ keyword is used to create a new method.
- 9. class Vector2D: x = 0.0 y = 0.0 # Creating a method named Set def Set(self, x, y): self.x = x self.y = y def Main(): # vec is an object of class Vector2D vec = Vector2D() # Passing values to the function Set # by using dot(.) operator. vec.Set(5, 6) print("X: " + vec.x + ", Y: " + vec.y) if __name__=='__main__': Main() Output: X: 5, Y: 6
- 10. Python In-built class functions
- 11. Inheritance Inheritance is the capability of one class to derive or inherit the properties from some another class. The benefits of inheritance are: It represents real-world relationships well. It provides reusability of a code. We don’t have to write the same code again and again. Also, it allows us to add more features to a class without modifying it. It is transitive in nature, which means that if class B inherits from another class A, then all the subclasses of B would automatically inherit from class A. Inheritance is defined as a way in which a particular class inherits features from its base class. Base class is also knows as ‘Superclass’ and the class which inherits from the Superclass is knows as ‘Subclass’
- 12. # Syntax for inheritance class derived-classname(superclass-name)
- 13. class Person(object): # class Person: of Python 3.x is same as defined here. def __init__(self, name): # Constructor self.name = name def getName(self): # To get name return self.name def isEmployee(self): # To check if this person is employee return False # Inherited or Sub class (Note Person in bracket) class Employee(Person): def isEmployee(self): # Here we return true return True # Driver code emp = Person(“Ram") # An Object of Person print(emp.getName(), emp.isEmployee()) emp = Employee(“Shyam") # An Object of Employee print(emp.getName(), emp.isEmployee()) OUTPUT: Ram False Shyam True
- 14. Explore more on Inheritance Type Thank You!