Question

I need to modify the following code (using Python3), where Groceries.csv is of following form (Item on 1st column, price on 2nd)

Stewing beef,15.45
Ground beef,11.29
Pork chops,11.72
Chicken,7.29
Bacon,7.12
Wieners,4.33
Canned salmon,5.68
Homogenized milk,5.79
Partly skimmed milk,5.20
Butter,4.99
Processed cheese slices,2.53
Evaporated milk,1.89
Eggs,3.11
Bread,2.74
Soda crackers,3.27
Macaroni,1.45
Flour,4.54
Corn flakes,5.72
Apples,4.71
Bananas,1.56
Oranges,3.70
...

a. In the function createPricesDict(), create a dictionary of each product mapped to its price.

b. Suppose we have another dictionary for our cart items, mapping each product to its quantity. Complete the function calculateShoppingCost() to get this dictionary as well as the dictionary created in the previous step and return the total amount that the customer owes.

=======

import csv

def calculateShoppingCost(productPrices, shoppingCart):
   finalCost = 0
   "*** Add your code in here ***"
   return finalCost


def createPricesDict(filename):
   productPrice = {}
   "*** Add your code in here ***"
   return productPrice


if __name__ == '__main__':
   prices = createPricesDict("Grocery.csv")
   myCart = {"Bacon": 2,
            "Homogenized milk": 1,
            "Eggs": 5}
   print("The final cost for our shopping cart is {}".format(calculateShoppingCost(prices, myCart)))

Answer 1

Following are the steps to read the file and populate the productPrices dictionary.

1. read the file using csv module reader method.
2. loop through all the rows/lines read from the file
3. insert the values in dictionary. first value is key and second is value

Following are the steps to calculate the final cost:

1. loop through the shopping cart
2. get the item quantity from item in shopping cart
3. get the item price from productPrices dictionary using item name as key
4. calculate the cost for that item by multiplying item quantity and item price
5. add the result in the final cost

Please refer the screenshot for indentation.

Code:

import csv

def calculateShoppingCost(productPrices, shoppingCart):
finalCost = 0

""" loop through shoppingCart item by item """
for item in shoppingCart.items():
""" calculate cost for the current item and add it in finalCost """

""" item quanitity """
itemQuantity = item[1]

""" get the item price from productPrices dictionary """
itemPrice = productPrices[item[0]]

""" multiple item quantity with item price and add the result in final cost """
finalCost = finalCost + itemQuantity * itemPrice

""" return the final cost """
return finalCost

def createPricesDict(filename):
productPrice = {}

""" open csv file in read mode """
with open(filename,'rt')as file:
"""
read the file content using csv module reader method
and get the list of all columns per line or row in the file
"""
productDetails = csv.reader(file)

""" loop through all the product detail lines read from the file """
for product in productDetails:
"""
first element in list is first column in csv file that is product name.
second element is the price of the product.
Add the product name as key and price as value in dictionary.
"""
productPrice[product[0]] = float(product[1])

""" return the productPrices dictionary """
return productPrice

if __name__ == '__main__':
prices = createPricesDict("Grocery.csv")
myCart = {"Bacon": 2,
"Homogenized milk": 1,
"Eggs": 5}
print("The final cost for our shopping cart is {}".format(calculateShoppingCost(prices, myCart)))

Output: