將單個鍵值對從一個字典移動到另一個

Question

我正在建立一個基本的python商店，其中包含商品及其價格的字典。 我正在為購物車使用字典，希望用戶能夠向購物車中添加項目。 為此，我旨在將鍵和值從產品字典復制到購物車字典。 我怎樣才能做到這一點？

products = {"Pencil": 1, "Notebook": 2, "Backpack": 3, "Pens": 2, "Markers": 5, "Whiteboard": 30}
cart = {}

def addToCart():
    productToAdd = input("What would you like to add? ")
    for k,v in products.items():
        if productToAdd == k:
            price = v
            cart[productToAdd] = cart[v]
            break

Answer 1

products = {"Pencil": 1, "Notebook": 2, "Backpack": 3, "Pens": 2, "Markers": 5, "Whiteboard": 30}
cart = {}

def addToCart():
    try:
        productToAdd = input("What would you like to add? ")
        cart[productToAdd]=products[productToAdd]
    except KeyError:
        print("No such product")

請注意，python區分大小寫，“ pencil”和“ Pencil”不同。 如果您確定產品首先要成為大寫字母，則可以使用

productToAdd = input("What would you like to add? ").title()

Answer 2

您可以使用dict.setdefault(key, default=None)
例：

def addToCart():
    productToAdd = input("What would you like to add? ")
    cart[productToAdd]=products.setdefault(productToAdd, 'No such product')

Answer 3

假設用戶將從該列表中選擇項目（尤其是從鍵中選擇），則：

products = {"Pencil": 1, "Notebook": 2, "Backpack": 3, "Pens": 2, "Markers": 5, 
"Whiteboard": 30}

cart = {}


def addToCart():
    productToAdd = input("What would you like to add? ")
    if not productToAdd.title() in products: # for removing caps confusion
        print('No such item')
    else: cart[productToAdd] = products[productToAdd]


>>> addToCart()
What would you like to add? Pencil
>>> cart
{'Pencil': 1}

Answer 4

我必須使用raw_input，否則將無法使用“ Pencil”之類的字符串。 這是復制鍵值對的方式。

products = {"Pencil": 1, "Notebook": 2, "Backpack": 3, "Pens": 2, "Markers": 5, "Whiteboard": 30}

cart = {}

def addToCart():
    productToAdd = raw_input("What would you like to add? ")
    for k,v in products.items():
        print(k)
        if productToAdd == k:
            cart[k] = v
            break

addToCart()
print(cart)