字典：四中基本集合之一，由鍵(key)值(value)對所組成

capital = {
    "United States": "Washington DC",
    "Japan": "Tokyo",
    "France": "Paris",
    "Russia": "Moscow"
}   

1.get()取得鍵值對

print(capital.get("Japan"))
print(capital.get("France"))


Tokyo
Paris

2.update()更新鍵值對

capital.update({"Germany": "Berlin"})
print(capital)


{'United States': 'Washington DC', 'Japan': 'Tokyo', 'France': 'Paris', 'Russia': 'Moscow', 'Germany': 'Berlin'}

3.pop()刪除鍵值對

capital.pop("United States")
print(capital)


{'Japan': 'Tokyo', 'France': 'Paris', 'Russia': 'Moscow', 'Germany': 'Berlin'}

4.values()獲得所有值

print(capital.values())


dict_values(['Washington DC', 'Tokyo', 'Paris', 'Moscow', 'Berlin'])

5.items()獲得所有鍵值對

print()capital.items())


dict_items([('United States', 'Washington DC'), ('Japan', 'Tokyo'), ('France', 'Paris'), ('Russia', 'Moscow'), ('Germany', 'Berlin')])

販賣機程式:
使用字典來儲存菜單及價格，使用while迴圈讓試用者選擇菜單項目，並加入購物車中
step1.製作菜單

menu = {
     "pizza": 300,
     "popcorn": 150,
     "chips": 60,
     "french fries": 80,
     "cola": 40,
     "juice": 35
}
print("  菜單:")
print("---------")
for item, price in menu.items():
    print(f"{item}: {price}")


  菜單:
---------
pizza: 300
popcorn: 150
chips: 60
french fries: 80
cola: 40
juice: 35

step2.讓使用者挑選品項，並加入購物車

menu = {
     "pizza": 300,
     "popcorn": 150,
     "chips": 60,
     "french fries": 80,
     "cola": 40,
     "juice": 35
}
print("  菜單:")
print("---------")
cart = []
total = 0
for item, price in menu.items():
    print(f"{item}: {price}")


while True:
    food = input("請輸入一個菜單選項（輸入done結束）")
    if food == "done":
        break
    elif menu.get(food) is None:
        print("沒有此項商品")
    else:
        cart.append(food)
        total += menu.get(food)
        print(food, end=" ")

print(f"總共： {total}元")


  菜單:
---------
pizza: 300
popcorn: 150
chips: 60
french fries: 80
cola: 40
juice: 35
請輸入一個菜單選項（輸入done結束）pizza
pizza 請輸入一個菜單選項（輸入done結束）candy
沒有此項商品
請輸入一個菜單選項（輸入done結束）chips
chips 請輸入一個菜單選項（輸入done結束）cola
cola 請輸入一個菜單選項（輸入done結束）done
總共： 400元