Question

嗨，我对python编码有点陌生，我已经准备好了伪代码但我无法正确编写python代码。这是我的伪代码：

Input(Item)
Item = Item.split()    
numberOfItem = count(Item)
until numberOfItem == 2:
   output("Please select two Item")
   input(Item)
itemCostDic = {"wood":200, "paper":100, "pen":10, "eraser":5}
specificItemCost = {}
for value in Item:
   specificItemCost[value] = itemCostDic[value]
totalItemCost = sum(specificItemCost.value)
print(totalItemCost)

我不确定如何在python代码中循环“直到”。

Answer 1

'Until'可以通过scrollable: { endless: true },等于python中的循环来实现：

while

但是您需要将while numberOfItem != 2: ...的变化值合并到循环本身中，以使其在某个时刻中断：

numberOfItem

Answer 2

while numberOfItem != 2:将循环播放，直到您获得2个项目。如果您最初有2个项目，则不会运行循环主体-当您在循环主体中中添加/删除列表中的内容并希望在其中的2个项目处停止时，将使用这种检查清单。

您需要以某种方式修改在循环中检查条件的值（或直接在同时进行while len(yourList) != 2:动态检查-lvl），否则循环将不断。

您使用字典细化代码以验证仅给出有效项。您可以将输入值与金额一起存储到第二个dict中，并在完成所有输入后将它们求和，如下所示：

（该代码结合了Asking the user for input until they give a valid response方法来验证用户输入）

itemCostDic = {"wood":200, "paper":100, "pen":10, "eraser":5}
print("Inventory:")
for k,v in itemCostDic.items():
    print( "   - {} costs {}".format(k,v))
print("Buy two:")
shoppingDic = {}
while len(shoppingDic) != 2:
   # item input and validation
   item = input("Item:").lower()
   if item not in itemCostDic:   # check if we have the item in stock
          print("Not in stock.")
          continue # jumps back to top of while
   if item in shoppingDic:       # check if already bought, cant buy twice
          print("You bought all up. No more in stock.")
          continue # jumps back to top of while

   # amount input and validation
   amount = input("Amount:")
   try:
          a = int(amount)         # is it a number? 
   except ValueError:             
          print("Not a number.")  
          continue # start over with item input, maybe next time user is wiser

   # add what was bought to the cart
   shoppingDic[item] = a

s = 0
print("Bought:")
for k,v in shoppingDic.items():
    print( "   - {} * {} = {}".format(k,v, itemCostDic[k]*v))
    s += itemCostDic[k]*v
print("Total: {:>12}".format( s))

输出：

Inventory:
   - wood costs 200
   - paper costs 100
   - pen costs 10
   - eraser costs 5
Buy two:
Item:socks
Not in stock.
Item:paper
Amount:5
Item:paper
You bought all up. No more in stock.
Item:pen
Amount:k
Not a number.
Item:pen
Amount:10
Bought:
   - paper * 5 = 500
   - pen * 10 = 100
Total:          600

没有金额：

itemCostDic = {"wood":200, "paper":100, "pen":10, "eraser":5}
print("Inventory:")
for k,v in itemCostDic.items():
    print( "   - {} costs {}".format(k,v))
print("Buy two:")
shoppingCart = set() # use a list if you can shop for 2 times paper
while len(shoppingCart) != 2:
   # item input and validation
   item = input("Item:").lower()
   if item not in itemCostDic:   # check if we have the item in stock
          print("Not in stock.")
          continue # jumps back to top of while
   if item in shoppingCart:       # check if already bought, cant buy twice
          print("You bought all up. No more in stock.")
          continue # jumps back to top of while

   # add what was bought to the cart
   shoppingCart.add(item)

s = 0
print("Sum of shopped items: {:>6}".format( sum ( itemCostDic[i] for i in shoppingCart) ))

输出：

Inventory:
   - wood costs 200
   - paper costs 100
   - pen costs 10
   - eraser costs 5
Buy two:
Item:socks
Not in stock.
Item:paper
Item:paper
You bought all up. No more in stock.
Item:wood
Sum of shopped items:    300

我有我的伪代码，但是我无法在python中编写循环之一

2 个答案: