Management Science
Welcome to your first interactive Python tutorial!
The Coffee Shop Calculator Problem
Imagine you just started working at a busy coffee shop called “Bean Counter.” On your first day, the manager asks you to help with various calculations: pricing drinks, applying discounts, calculating tips, and formatting receipts. The old calculator is broken, and they need a better system anyway. Lucky for them, you know Python!
In this tutorial, we’ll learn about variables and basic data types to build your own coffee shop calculator system. By the end, you’ll be able to handle any calculation the shop throws at you!
If a cell is marked with YOUR CODE BELOW, you are expected to write your code in that cell.
Variables are like labeled containers that store information. In our coffee shop, we need to keep track of prices, customer names, order quantities, and more. Variables allow us to store this information in a way that we can easily access and update it later.
# Variables are created by giving them a name and a value
coffee_price = 4.50
customer_name = "Alex"
cups_ordered = 3
shop_open = True
print(f"Customer {customer_name} ordered {cups_ordered} coffees at ${coffee_price} each")Customer Alex ordered 3 coffees at $4.5 eachCreate three variables for a new order:
latte_price should be 5.25customer should be “Maria”quantity should be 2shop_closed = False# YOUR CODE BELOW# Test your answer
assert latte_price == 5.25, "The latte_price should be 5.25"
assert customer == "Maria", "The customer should be 'Maria'"
assert quantity == 2, "The quantity should be 2"
assert shop_closed == False, "The shop should be open"
print("Perfect! You've created your first variables for the coffee shop!")Variables can change! A customer changed their mind and wants 4 lattes instead of 2. Update the quantity variable to 4 and create a new variable total_order that stores the total price (latte_price multiplied by quantity).
# YOUR CODE BELOW
# Assume latte_price = 5.25 and quantity = 2 from previous exercise
# Tip: Just overwrite these old values
# Then calculate: total_order = latte_price * quantity# Test your answer
assert quantity == 4, "The quantity should be updated to 4"
assert total_order == 21.0, "The total_order should be 21.0 (5.25 * 4)"
print("Excellent! You can update variables and create new ones from existing values!")Python has different types of data. The three most common are:
# Different data types in our coffee shop
cups_sold = 150 # int - whole number
price = 4.99 # float - decimal number
shop_name = "Bean Counter" # str - text
is_open = True # bool - true or false
# Python can tell you the type of any variable
print(f"cups_sold is a {type(cups_sold)}")
print(f"price is a {type(price)}")
print(f"shop_name is a {type(shop_name)}")
print(f"is_open is a {type(is_open)}")cups_sold is a <class 'int'>
price is a <class 'float'>
shop_name is a <class 'str'>
is_open is a <class 'bool'>Common Mistake: Mixing up numbers and text that looks like numbers!
quantity = "5" # This is text, not a number!
quantity * 2 # This would give "55" not 10!Create variables of each type for our coffee shop:
daily_customers (int): 85 customers visited todayaverage_tip (float): 2.50 dollars average tipbest_seller (str): “Caramel Macchiato”# YOUR CODE BELOW# Test your answer
assert daily_customers == 85 and type(daily_customers) == int, "daily_customers should be the integer 85"
assert average_tip == 2.50 and type(average_tip) == float, "average_tip should be the float 2.50"
assert best_seller == "Caramel Macchiato" and type(best_seller) == str, "best_seller should be the string 'Caramel Macchiato'"
print("Great job! You understand the different data types!")Sometimes we need to convert between types. A customer’s loyalty card bonus points were entered as text “1234” but we need it as a number to do calculations.
Convert the string card_points = "1234" to an integer and create a new variable new_points that adds 100 bonus points to it.
You can use the int() function to convert a string to an integer or use the float() function to convert a string to a float.
# YOUR CODE BELOW
card_points = "1234"# Test your answer
assert card_points == 1234, "card_points should be 1234 as an integer"
assert new_points == 1334, "new_points should be 1334 (1234 + 100)"
print("Perfect! You can convert between data types!")Now let’s use Python’s arithmetic operations to handle coffee shop calculations!
# Basic arithmetic operations
espresso_price = 3.50
shots = 2
# Addition and multiplication
double_espresso = espresso_price * shots
with_tip = double_espresso + 1.50
# Division and subtraction
change = 20.00 - with_tip
price_per_shot = double_espresso / shots
print(f"Double espresso: ${double_espresso}")
print(f"With tip: ${with_tip}")
print(f"Change from $20: ${change}")
print(f"Price per shot: ${price_per_shot}")Double espresso: $7.0
With tip: $8.5
Change from $20: $11.5
Price per shot: $3.5+ Addition- Subtraction* Multiplication/ Division** Exponentiation (power)// Floor division (rounds down)% Modulo (remainder)A group orders:
Calculate the subtotal, then add 19% tax to get the total_with_tax.
To add 19% tax to a value, you can multiply by 1.19.
# YOUR CODE BELOW# Test your answer
import math
assert math.isclose(subtotal, 30.20, rel_tol=0.01), "Subtotal should be 30.20"
assert math.isclose(total_with_tax, 30.20*1.19, rel_tol=0.01), "Total with tax should be 35.94"
print("Excellent calculation! You've mastered basic arithmetic!")The group wants to split the bill evenly among 4 people. Calculate:
per_person)dollars) and cents (cents) each person needs. Provide each as variable.You could use // for floor division and % for remainder, but you don’t need to do that as other solutions are possible. If you want to round the cents, you can use the round() function.
# YOUR CODE BELOW
# Assume total_with_tax = 32.616 from previous exercise# Test your answer
assert math.isclose(per_person, 8.154, rel_tol=0.01), "Each person should pay 8.154"
assert dollars == 8, "Each person needs 8 dollars"
assert cents == 15, "Each person needs 15 cents (rounded)"
print("Great work! You can split bills and handle money calculations!")F-strings make it easy to create formatted output - perfect for receipts and displays!
# F-strings let you embed variables and expressions in text
item = "Flat White"
price = 4.25
quantity = 2
total = price * quantity
# Basic f-string
receipt = f"Item: {item}, Quantity: {quantity}, Total: ${total}"
print(receipt)
# Formatting numbers
formatted_receipt = f"""
╔══════════════════════════╗
║ BEAN COUNTER ║
╠══════════════════════════╣
║ {item:<16} {quantity:2d} ║
║ Price: ${price:>6.2f} ║
║ Total: ${total:>6.2f} ║
╚══════════════════════════╝
"""
print(formatted_receipt)Item: Flat White, Quantity: 2, Total: $8.5
╔══════════════════════════╗
║ BEAN COUNTER ║
╠══════════════════════════╣
║ Flat White 2 ║
║ Price: $ 4.25 ║
║ Total: $ 8.50 ║
╚══════════════════════════╝
f before the string or use incorrect syntax within the curly braces.{variable:.2f} - Show 2 decimal places{variable:10} - Use 10 characters of space{variable:<10} - Left align in 10 spaces{variable:>10} - Right align in 10 spaces{variable:^10} - Center in 10 spacesCreate a formatted receipt for a coffee order with these variables:
coffee_type = "Americano"size = "Large"price = 3.75Create a variable called receipt with the format: “Order: [size] [coffee_type] - $[price with 2 decimal places]”
Use an f-string with {price:.2f} to format the price with exactly 2 decimal places.
# YOUR CODE BELOW# Test your answer
assert receipt == "Order: Large Americano - $3.75", "Receipt should be 'Order: Large Americano - $3.75'"
print("Perfect! You've created your first formatted string!")Congratulations! You’ve successfully learned the fundamentals of Python programming!
You’ve learned:
You can now handle any calculation at Bean Counter coffee shop! From calculating bills and splitting checks to creating professional receipts, you have all the basic tools you need.
Remember:
Next up: In the next tutorial, we’ll learn about lists and loops to handle multiple orders at once and analyze daily sales data!