Describing Similar Objects

Sometimes, the objects that we are describing are so similar that only values of the properties differ.

Object 3 is a Mobile

Properties

camera : 13 MP

storage : 16 GB

battery life : 21 Hrs

ram : 3 GB

and so on ...

Object 4 is a Mobile

Properties

camera : 64 MP

storage : 128 GB

battery life : 64 Hrs

ram : 6 GB

and so on ...

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In this case, the objects that we describe have completely the same set of properties like camera, storage, etc.

Template

For objects that are very similar to each other (objects that have the same set of actions and properties), we can create a standard Form or Template that can be used to describe different objects in that category.

Mobile Template

Model :

Camera:

Storage:

Does it have a Face Unlock? Yes | No

Filled Template

Model : iPhone 12 Pro

Camera: 64MP

Storage: 128GB

Does it have a Face Unlock? Yes

Bundling Data

While modeling real-life objects with object oriented programming, we ensure to bundle related information together to clearly separate information of different objects.

Bundling of related properties and actions together is called Encapsulation.

Classes can be used to bundle related properties and actions.

Defining a Class

To create a class, use the keyword

class

Special Method

In Python, a special method

__init__

is used to assign values to properties.

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class Mobile:

def __init__(self, model, camera):

self.model = model

self.camera = camera

PYTHON

Properties & Values

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class Mobile:

def __init__(self, model, camera):

self.model = model

self.camera = camera

def make_call(self, number):

print("calling..")

PYTHON

In the above example,

model

and

camera

are the properties and values are which passed to the

__init__

method.

Action

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class Mobile:

def __init__(self, model, camera):

self.model = model

self.camera = camera

def make_call(self, number):

print("calling..")

PYTHON

In the above example, the below function is an action

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def make_call(self, number):

print("calling..")

PYTHON

In OOP terminology, properties are referred as attributes actions are referred as methods

Using a Class

To use the defined class, we have to instantiate it. A class is like a blueprint, while its instance is based on that class with actual values.

Instance of Class

Syntax for creating an instance of class looks similar to function call.

An instance of class is Object.

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class Mobile:

def __init__(self, model, camera):

self.model = model

self.camera= camera

mobile_obj = Mobile(

"iPhone 12 Pro",

"12 MP")

print(mobile_obj)

PYTHON

Class Object

An object is simply a collection of attributes and methods that act on those data.

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class Mobile:

def __init__(self, model, camera):

self.model = model

self.camera= camera

mobile_obj = Mobile(

"iPhone 12 Pro",

"12 MP")

print(mobile_obj)

PYTHON

Method Arguments & Return Values

Similar to functions, Methods also support positional, keyword & default arguments and also return values.

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class Mobile:

def __init__(self, model, camera):

self.model = model

self.camera= camera

def make_call(self,number):

return "calling..{}".format(number)

PYTHON

Instance Methods of Class

For instance method, we need to first write

self

in the function definition and then the other arguments.

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class Mobile:

def __init__(self, model, camera):

self.model = model

self.camera= camera

def make_call(self,number):

print("calling..{}".format(number))

mobile_obj = Mobile("iPhone 12 Pro", "12 MP")

mobile_obj.make_call(9876543210)

PYTHON

Output

calling..9876543210

Multiple Instances

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class Mobile:

def __init__(self, model, camera):

self.model = model

self.camera= camera

def make_call(self,number):

print("calling..{}".format(number))

mobile_obj1 = Mobile("iPhone 12 Pro", "12 MP")

print(id(mobile_obj1))

mobile_obj2 = Mobile("Galaxy M51", "64 MP")

print(id(mobile_obj2))

PYTHON

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Output

139685004996560

139685004996368

Type of Object

The class from which object is created is considered to be the type of object.

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class Mobile:

def __init__(self, model, camera):

self.model = model

self.camera = camera

obj_1 = Mobile("iPhone 12 Pro", "12 MP")

print(type(obj_1))

PYTHON

Output

<class '__main__.Mobile'>