Assignment5_3.py

'''
Created on 19.5.2015

    Improve your program for problem 1 so that if negative numbers are given as the amount
    or unit price the program will raise an Arithmetic exception.
    
@author: e1201757
'''

import os

DB_PATH = 'product_db.txt'

def writeToFile(content, filePath):
    file = open(filePath, 'a+')
    file.write(content + '\n')
    file.close()

def readFromFile(filePath):
    if os.path.exists(filePath):
        file = open(filePath, 'r')
        content = file.read().split('\n')
        content.pop()
        productsList = []
        for product in content:
            productDict = {}
            details = product.split(';')
            productDict['name'] = details[0]
            productDict['unit_price'] = details[1]
            productDict['amount'] = details[2]
            productsList.append(productDict)
        file.close()
        return productsList
    return []
        
def inputProductsFromConsole():
    text = ''
    while True:
        print('Please enter product data (name;unit price;amount), and use \';\' to separate(enter \'q\' to quit).')
        print('For example: Apple;2;100')
        text =  input('New product:').replace(' ', '')
        if validateProduct(text):
            writeToFile(text, DB_PATH)
            input('New data have been saved. Enter \'ENTER\' to continue.')
            print('---------------------------------------')    
        elif text == 'q': 
            print('---------------------------------------')
            break
        else: 
            print('Wrong Format!')
            input('Enter \'ENTER\' to continue.')
            print('---------------------------------------')
        
def validateProduct(text):
    details = text.split(';')    
    if len(details) == 3:
        try:
            if eval(details[1]) < 0 or eval(details[2]) < 0:
                raise ArithmeticError
        except ArithmeticError:
            print ('Error: negative numbers given as the amount or unit price are not allowed!')
        else:
            return True
    return False
    
def searchProducts(criteria, value):
    productsList = readFromFile(DB_PATH)
    correctProducts = []
    print('Search Result(s):')
    for productDict in productsList:
        if productDict[criteria] == value:
            correctProducts.append(productDict)
    if correctProducts != []:
        for productDict in correctProducts:
            printProduct(productDict)
    else: print('No Product has been found!\n')
    input('Enter \'ENTER\' to continue.')
    print('---------------------------------------')
        
def showAllProducts(filePath):
    productsList = readFromFile(filePath)
    if productsList!=[]:
        for productDict in productsList:
            printProduct(productDict)
    else: print('No product has been found!\n')     
    input('Enter \'ENTER\' to continue.')  
    print('---------------------------------------') 
        
def printProduct(productDict):
    print('name: ' + productDict['name'])
    print('unit price: ' + productDict['unit_price'])
    print('amount: ' + productDict['amount'])
    print('---------------------------------------')

if __name__ == '__main__':
    while True:
        print('******Products Information System******\n\n1. Enter new product data.\n2. Search by criteria in products database \n3. Show all products infomation.\n4. Quit.\n')
        choice = input('Please select:')
        print('---------------------------------------')
        if choice == '1':
            inputProductsFromConsole()
        elif choice == '2':
            criteria = input('Enter the criteria to search(name/unit_price/amount):')
            value = input('Enter the value:')
            searchProducts(criteria, value)
        elif choice == '3':
            showAllProducts(DB_PATH)
        elif choice == '4':
            print('Bye bye!')
            break
        else:
            print('Error input! Please enter a number from 1 to 4!\n')
            print('---------------------------------------')