Table of contents
Introduction
In this lab you will be presented with a menu ordering system which will allow users to input three choices for a select menu. You are tasked with completing the menu system so that it returns and calculates the final bill for the user.
Objectives
Create new functions to solve specific problems.
Gain experience of using for loops to iterate over different data collections.
Create and use data structures to store, retrieve and loop over data.
Instructions
Step 1: Open the script ordering_system.py present inside the project folder.
Step 2: Run the script and, when requested, enter in the three products of your choice based on the menu - 1 = espresso, 2 = coffee etc.
Step 3: To run the script, open the terminal and execute the command below.
Step 4: Extend the script to have a new function called calculate_subtotal. It should accept one argument which is the order list and return the sum of the prices of the items in the order list.
Step 5: Implement calculate_tax() which calculates the tax of the subtotal. The tax percentage is 15% of overall bill.
Step 6: Implement summarize_order() which returns a list of the names of the items that the customer ordered and the total amount (including tax) that they have to pay. The orders should show the name and price.
Solution
menu = {
1: {"name": 'espresso',
"price": 1.99},
2: {"name": 'coffee',
"price": 2.50},
3: {"name": 'cake',
"price": 2.79},
4: {"name": 'soup',
"price": 4.50},
5: {"name": 'sandwich',
"price": 4.99}
}
def calculate_subtotal(order):
""" Calculates the subtotal of an order
[IMPLEMENTED]
1. Add up the prices of all the items in the order and return the sum
Args:
order: list of dicts that contain an item name and price
Returns:
float = The sum of the prices of the items in the order
"""
print('Calculating bill subtotal...')
### WRITE SOLUTION HERE
subtotal = 0 # initialize a variable to store the sum
for item in order: # loop over the list of dictionaries
subtotal += item["price"] # add the price of each item to the sum
return subtotal # return the sum
def calculate_tax(subtotal):
""" Calculates the tax of an order
[IMPLEMENTED]
1. Multiply the subtotal by 15% and return the product rounded to two decimals.
Args:
subtotal: the price to get the tax of
Returns:
float - The tax required of a given subtotal, which is 15% rounded to two decimals.
"""
print('Calculating tax from subtotal...')
### WRITE SOLUTION HERE
tax = subtotal * 0.15 # multiply the subtotal by 0.15
tax = round(tax, 2) # round the result to two decimal places
return tax # return the tax
def summarize_order(order):
""" Summarizes the order
[IMPLEMENTED]
1. Calculate the total (subtotal + tax) and store it in a variable named total (rounded to two decimals)
2. Store only the names of all the items in the order in a list called names
3. Return names and total.
Args:
order: list of dicts that contain an item name and price
Returns:
tuple of names and total. The return statement should look like
return names, total
"""
print('Summarizing order...')
### WRITE SOLUTION HERE
subtotal = calculate_subtotal(order) # call calculate_subtotal function
tax = calculate_tax(subtotal) # call calculate_tax function
total = round(subtotal + tax, 2) # calculate total by adding subtotal and tax and rounding to two decimals
names = [] # initialize an empty list to store names
for item in order: # loop over the list of dictionaries
names.append(item["name"]) # append the name of each item to the list
return names, total # return a tuple of names and total
