Python Classes and Objects

 

Classes and Objects

Attributes of an Object

Attributes can be set or accessed using

.

(dot) character.

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class Mobile:

def __init__(self, model, storage):

self.model = model

self.storage = storage

obj = Mobile("iPhone 12 Pro", "128GB")

print(obj.model)

PYTHON

Output

iPhone 12 Pro

Accessing in Other Methods

We can also access and update properties in other methods.

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class Mobile:

def __init__(self, model):

self.model = model

def get_model(self):

print(self.model)

obj_1 = Mobile("iPhone 12 Pro")

obj_1.get_model()

PYTHON

Output

iPhone 12 Pro

Updating Attributes

It is recommended to update attributes through methods.

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class Mobile:

def __init__(self, model):

self.model = model

def update_model(self, model):

self.model = model

obj_1 = Mobile("iPhone 12")

print(obj_1.model)

obj_1.update_model("iPhone 12 Pro")

print(obj_1.model)

PYTHON

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Output

iPhone 12

iPhone 12 Pro

Modeling Class

Let’s model the scenario of shopping cart of ecommerce site.

The features a cart should have

• can add an item
• can remove an item from cart
• update quantity of an item
• to show list of items in cart
• to show total price for the items in the cart

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class Cart:

def __init__(self):

self.items = {}

self.price_details = {"book": 500, "laptop": 30000}

def add_item(self, item_name, quantity):

self.items[item_name] = quantity

def remove_item(self, item_name):

del self.items[item_name]

def update_quantity(self, item_name, quantity):

self.items[item_name] = quantity

def get_cart_items(self):

cart_items = list(self.items.keys())

return cart_items

def get_total_price(self):

total_price = 0

for item, quantity in self.items.items():

total_price += quantity * self.price_details[item]

return total_price

cart_obj = Cart()

cart_obj.add_item("book", 3)

cart_obj.add_item("laptop", 1)

print(cart_obj.get_total_price())

cart_obj.remove_item("laptop")

print(cart_obj.get_cart_items())

cart_obj.update_quantity("book", 2)

print(cart_obj.get_total_price())

 

PYTHON

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Output

31500

['book']

1000