Python-Design-Patterns 3-tier
3-tier Model
Python-Design-Patterns 3-tier
# file: '3-tier.py'
#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
*TL;DR80
Separates presentation, application processing, and data management functions.
"""
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
3-tier.py
