Python programming : Abstract classes interfaces

Abstract Classes And
Interfaces
Team Emertxe

Introduction
Example:
To understand that Myclass method is shared by all objects
class Myclass:
def calculate(self, x):
print("Square: ", x * x)
#All objects share same calculate() method
obj1 = Myclass()
obj1.calculate(2)
obj2 = Myclass()
obj2.calculate(3)
obj3 = Myclass()
obj3.calculate(4)

Question

What If?

Object-1 wants to calculate square value

Object-2 wants to calculate square root

Object-3 wants to calculate Cube

Solution-1

Define, three methods in the same class

calculate_square()

calculate_sqrt()

calculate_cube()

Disadvantage:

All three methods are available to all the objects which is not advisable

Solution-2
calculate(x):
no body
calculate(x):
square of x
calculate(x):
sqrt of x
calculate(x):
cube of x
Obj1 Obj2 Obj3
Myclass
Sub1 Sub2 Sub3

Abstract Method & Class

Abstract Method

- Is the method whose action is redefined in sub classes as per the requirements

of the objects

- Use decorator @abstractmethod to mark it as abstract method

- Are written without body

Abstract Class

- Is a class generally contains some abstract methods

- PVM cannot create objects to abstract class, since memory needed will not be

known in advance

- Since all abstract classes should be derived from the meta class ABC which belongs to
abc(abstract base class) module, we need to import this module

- To import abstract class, use

- from abc import ABC, abstractmethod

OR

- from abc import *

Program-1
#To create abstract class and sub classes which implement the abstract method of the
abstract class
from abc import ABC, abstractmethod
class Myclass(ABC):
@abstractmethod
pass
#Sub class-1
class Sub1(Myclass):
print("Square: ", x * x)
Obj1 = Sub1()
Obj1.calculate(2)
Obj2 = Sub2()
Obj2.calculate(16)
Obj3 = Sub3()
Obj2.calculate(3)
#Sub class-2
import math
print("Square root: ", math.sqrt(x))
#Sub class-3
print("Cube: ", x * x * x)

Example-2

Maruthi, Santro, Benz are all objects of class Car
Registration no. - All cars will have reg. no.
- Create var for it
Fuel Tank - All cars will have common fule tank
- Action: Open, Fill, Close
Steering - All cars will not have common steering
say, Maruthi uses- Manual steering
Santro uses - Power steering
- So define this as an Abstract Method
Brakes - Maruthi uses hydraulic brakes
- Santro uses gas brakes
- So define this as an Abstract Method

Program-2
#Define an absract class
from abc import *
class Car(ABC):
def __init__(self, reg_no):
self.reg_no = reg_no
def opentank(self):
print("Fill the fuel for car with reg_no: ",
self.reg_no)
@abstractmethod
def steering(self):
pass
@abstractmethod
def braking(self):
pass
#Define the Maruthi class
from abstract import Car
class Maruthi(Car):
def steering(self):
print("Maruthi uses Manual steering")
def braking(self):
print("Maruthi uses hydraulic braking system")
#Create the objects
Obj = Maruthi(123)
Obj.opentank()
Obj.steering()
Obj.braking()

Interfaces

Abstract classes contains both,

- Abstract methods

- Concrete Methods

Interfaces is also an Abstract class, but contains only

- Abstract methods

Plus point of Interface.

- Every sub-class may provide its own implementation for the abstract methods

Interfaces
Program-1
from abc import *
class Myclass(ABC):
@abstractmethod
def connect(self):
pass
@abstractmethod
def disconnect(self):
pass
#Define Database
class Database:
str = input("Enter the database name: ")
#Covert the string into the class name
classname = globals()[str]
#create an object
x = classname()
#Call methods
x.connect()
x.disconnect()
#Sub-Class:1
class Oracle(Myclass):
def connect(self):
print("Connecting to oracle database...")
print("Disconnecting from oracle
database...")
#Sub-Class:2
class Sybase(Myclass):
def connect(self):
print("Connecting to sybase database...")
print("Disconnecting from sybase
database...")

Interfaces
Program-2
from abc import *
class Myclass(ABC):
@abstractmethod
def putdata(self, text):
pass
@abstractmethod
pass
#Define Printer
class Printer:
str = input("Enter the printer name: ")
#Covert the string into the class name
classname = globals()[str]
#create an object
x = classname()
#Call methods
x.putdata("Sending to printer")
x.disconnect()
#Sub-Class:1
class IBM(Myclass):
print(text)
print("Disconnecting from IBM printer...")
#Sub-Class:2
class Epson(Myclass):
print(text)
print("Disconnecting from Epson printer...")

Python programming : Abstract classes interfaces

Recommended

More Related Content

What's hot (20)

Similar to Python programming : Abstract classes interfaces (20)

More from Emertxe Information Technologies Pvt Ltd (20)

Recently uploaded (20)

Python programming : Abstract classes interfaces