需求：

　　選擇商品，結算所選的商品

#目前總資產
asset_all = 0
#所選商品總價
all_price = 0
#購物車列表，目前已選擇商品
#每個元素的結構："商品名":{‘price‘:"單個商品價格",‘num‘:"購買數量"}
car_dict = {}

i1 = input("請輸入總資產：")
asset_all += int(i1)

goods = [
    {"name":"電腦","price":1999},
    {"name":"鼠標","price":50},
    {"name":"鍵盤","price":40},
    {"name":"U盤","
 
price":20}
]
#循環輸出商品信息
for k,i in enumerate(goods,1):
    print(k,i[‘name‘],i[‘price‘])

#選擇商品將其加入購物車
while True:
    i2 = input("請選擇商品(q結算)：")
    if i2.lower() == ‘q‘:
        break
    i2 -= 1
    name = goods[i2]["name"]
    price = goods[i2]["price"]
    if name in car_dict.keys():
        car_dict[name][
 
"num"] += 1
    else:
        car_dict[name] = {"price":price,"num":1}

#計算購物車裏所有商品的總價格
for i,j in car_dict.items():
    p = j["price"]
    n = j["num"]
    all_sum = p * n
    all_price += all_sum

#判斷是否能購買商品
if all_price > asset_all:
    print("余額不足，請充值")
else:
    asset_all -= all_price
    print
 
("購買成功")
    car_dict.clear()

python入門之實例-購買商品