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19. Working with Dictionaries and while Loops

By Bernd Klein. Last modified: 16 Aug 2021.

Introduction

Coffee Vending Machine

In this chapter of our Python tutorial we assume that you are familiar with Python dictionaries and while loops, as we have discussed them in our chapters Dictionaries and Loops.

We included this chapter to provide the learners with additional exercises of both dictionaries and while loops. The focus lies on nested dictionaries, in our case dictionaries of dictionaries. From the experiences of my courses, I know that these often cause special difficulties in particular for beginners.

This chapter is also about coffee, tea and other hot drinks, whose consumption we manage using Python Dictionaries.

Coffee, Dictionary and a Loop

coffee_list = {"Peter": 0, 
               "Eva": 0, 
               "Franka": 0}

while True:
    name = input("Name: ")
    if name == "":
        break
    coffee_list[name] += 1
    print(coffee_list[name])
    
print("coffee list: ", coffee_list)

OUTPUT:

1
1
2
1
coffee list:  {'Peter': 2, 'Eva': 1, 'Franka': 1}
coffee_list = {"Peter": 0, 
               "Eva": 0, 
               "Franka": 0}
tea_list = {"Peter": 0, 
            "Eva": 0, 
            "Franka": 0}

while True:
    name = input("Name: ")
    if name == "":
        break
    getränk = input("Beverage (coffee/tea): ")
    if getränk.lower() == "coffee":
        coffee_list[name] += 1
        print(coffee_list[name])
    elif getränk.lower() == "tea":
        tea_list[name] += 1
        print(tea_list[name])
        
print("coffee list: ", coffee_list)
print("tea list: ", tea_list)

OUTPUT:

1
1
1
coffee list:  {'Peter': 1, 'Eva': 0, 'Franka': 0}
tea list:  {'Peter': 0, 'Eva': 1, 'Franka': 1}
list_of_beverages = {"Peter": {"tea": 0, 
                           "coffee": 0}, 
                 "Eva": {"tea": 0, 
                         "coffee": 0}, 
                 "Franka": {"tea": 0, 
                            "coffee": 0}}

while True:
    name = input("Name: ").capitalize()
    if name == "":
        break
    if name not in list_of_beverages:   
        antwort = input("Shall we include " + name + " in the list? (y/n)")
        if antwort.lower() in ["y", "yes"]:
            list_of_beverages[name] = {"tea": 0, "coffee": 0}
        else:
            print(name + " cannot have a drink!")
            continue
    drink = input("Beverage (coffee/tea): ")
    list_of_beverages[name][drink] += 1
print(list_of_beverages)

OUTPUT:

Eve cannot have a drink!
{'Peter': {'tea': 0, 'coffee': 1}, 'Eva': {'tea': 1, 'coffee': 0}, 'Franka': {'tea': 1, 'coffee': 0}}
supermarket = {"milk": {"quantity": 20, "price": 1.19},
               "biscuits":  {"quantity": 32, "price": 1.45},
               "butter":  {"quantity": 20, "price": 2.29},
               "cheese":  {"quantity": 15, "price": 1.90},
               "bread":  {"quantity": 15, "price": 2.59},
               "cookies":  {"quantity": 20, "price": 4.99},
               "yogurt": {"quantity": 18, "price": 3.65},
               "apples":  {"quantity": 35, "price": 3.15},
               "oranges":  {"quantity": 40, "price": 0.99},
               "bananas": {"quantity": 23, "price": 1.29}}
total_value = 0
for article, numbers in supermarket.items():
    quantity = numbers["quantity"]
    price = numbers["price"]
    product_price = quantity * price
    article = article + ':'
    print(f"{article:15s} {product_price:08.2f}")
    total_value += product_price
print("="*24)   
print(f"Total sum:      {total_value:08.2f}")
    

OUTPUT:

milk:           00023.80
biscuits:       00046.40
butter:         00045.80
cheese:         00028.50
bread:          00038.85
cookies:        00099.80
yogurt:         00065.70
apples:         00110.25
oranges:        00039.60
bananas:        00029.67
========================
Total sum:      00528.37