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3-tier.py

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#!/usr/bin/env python

# -*- coding: utf-8 -*-

class Data(object):

""" Data Store Class """

products = {

'milk': {'price': 1.50, 'quantity': 10},

'eggs': {'price': 0.20, 'quantity': 100},

'cheese': {'price': 2.00, 'quantity': 10}

}

def __get__(self, obj, klas):

print ("(Fetching from Data Store)")

return {'products': self.products}

class BusinessLogic(object):

""" Business logic holding data store instances """

data = Data()

def product_list(self):

return self.data['products'].keys()

def product_information(self, product):

return self.data['products'].get(product, None)

class Ui(object):

""" UI interaction class """

def __init__(self):

self.business_logic = BusinessLogic()

def get_product_list(self):

print('PRODUCT LIST:')

for product in self.business_logic.product_list():

print(product)

print('')

def get_product_information(self, product):

product_info = self.business_logic.product_information(product)

if product_info:

print('PRODUCT INFORMATION:')

print('Name: {0}, Price: {1:.2f}, Quantity: {2:}'.format(

product.title(), product_info.get('price', 0),

product_info.get('quantity', 0)))

else:

print('That product "{0}" does not exist in the records'.format(

product))

def main():

ui = Ui()

ui.get_product_list()

ui.get_product_information('cheese')

ui.get_product_information('eggs')

ui.get_product_information('milk')

ui.get_product_information('arepas')

if __name__ == '__main__':

main()

### OUTPUT ###

# PRODUCT LIST:

# (Fetching from Data Store)

# cheese

# eggs

# milk

# (Fetching from Data Store)

# PRODUCT INFORMATION:

# Name: Cheese, Price: 2.00, Quantity: 10

# (Fetching from Data Store)

# PRODUCT INFORMATION:

# Name: Eggs, Price: 0.20, Quantity: 100

# (Fetching from Data Store)

# PRODUCT INFORMATION:

# Name: Milk, Price: 1.50, Quantity: 10

# (Fetching from Data Store)

# That product "arepas" does not exist in the records