Python

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The Python Programming Language at Champak's World
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Python

Creating Classes in Python

We start with the obvious question?

What is a class

Imagine that you are developing a piece of machinery. Maybe a car. How would you go about developing it?

 

First of all we will define the car as a finished product. List out all the components of the car.

Steering wheel, wheels, tyre, seats, doors etc.

Furthermore we will divide these smaller components into still smaller components.

Thus the steering wheel itself would be  collection of components. These smaller components would be made up of still smaller components and so on. All these components are Objects. This is Object Oriented Programming.

How will these Objects be made?

We will make designs of these objects on paper and write down the parts needed and the functions of the parts.

Car

{

  1. Steering Wheel
    1. Steers the car by rotating the front wheels.
  2. Wheels
    1. Front Wheel
    2. Rear Wheel
  3. Doors

 

 

 

A class in Python is created by using the class keyword.

We shall write

class ClassName:

Body of the class.


class Book:
#Class Body Here

Next, we will create a constructor and a toString method. The constructor is used to create an object of the class. In Python the constructor is written as __init__ , and will contain a list of parameters start with self. Self is the name of the this pointer in Python.


class Book:
def __init__(self,bookname,bookprice,booksubject):
self.bookname=bookname
self.bookprice=bookprice
self.booksubject=booksubject
b1=Book("Basic C",150,"C")
print(b1)

Output

<__main__.Book object at 0x000000955E661198>

 

To get a proper output create a __str__ method in the class that returns a string.

 


class Book:
def __init__(self,bookname,bookprice,booksubject):
self.bookname=bookname
self.bookprice=bookprice
self.booksubject=booksubject
def __str__(self):
return "Name={0}, Price={1}, Subject={2}".format(self.bookname,self.bookprice,self.booksubject)
b1=Book("Basic C",150,"C")
print(b1)

Output
Name=Basic C, Price=150, Subject=C

end

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