Python：在列表中查找项目

Question

So I'm having trouble figuring out how to write this. The part I'm having trouble with is trying to figure out a way to find any match that is less than the max cost, and I can't figure out how to find the itemtype and max cost values in a list in another list.

The question: Find an item

When the user selects 2 to find an item, they should be prompted with the item type, and the maximum price they are willing to pay for the item. Your code should then search the list and return the first item with the correct type and a cost that is less than or equal to
the price that the user will pay.

Use the following text in your prompts: "Enter the item type-b,m,d,t,c:" <--these are the only options for item type. "Enter the maximum item cost:"

For example, if the user types b and 50, they want a bicycle and are willing to pay up to
$50 for it.

Your program should find the first bicycle in the list that sells for $50 or less.
If a match is found, print “Sold for”

Use the following print statement: print "Sold", itemType, "for", itemCost where itemType and itemCost are variables that store the type of the item and its cost.

The itemType is one of the following: bike, microwave, dresser, truck, or chicken.

The itemCost is the actual item cost, not what the user is willing to pay.

The item should then be removed from the list.
If the item is not found, do nothing.

This is what I have so far:

p=2
a=[['b', 40], ['c', 330], ['m', 50], ['d', 70], ['t', 85]]
while p == 2:
    if len(a) > 0:
        itemtype = raw_input("Enter the item type-b,m,d,t,c:")
        maxcost = raw_input("Enter the maximum item cost:")
        x = [itemtype, maxcost]

Notes: the list a is just a reference while I figure out how to do it. The real a will be changed by the user. Thanks.

Answer 1

Use a dictionary, storing the items as keys and lists of values, you can use bisect to efficiently find the closest price to the user:

def purchase():
    from bisect import bisect_left
    data = {"b": [10, 20, 30, 40], "c": [100, 200, 330], "m": [20, 40, 50], "d": [70, 80, 90], "t": [50, 85, 100]}
    for _ in range(2):
        item_type = raw_input("Enter the item type-b,m,d,t,c:")
        max_cost = int(input("Enter the maximum item cost:"))
        v = data[item_type]
        ind = bisect_left(v, max_cost, hi=len(v) - 1)
        if v[ind] <= max_cost:
            print("Sold for {}".format(v[ind]))
            v.remove(v[ind])
        else:
            print("Sorry, cheapest is {}".format(v[0]))

Demo:

In [2]: purchase()
Enter the item type-b,m,d,t,c:b
Enter the maximum item cost:10
Sold for 10
Enter the item type-b,m,d,t,c:b
Enter the maximum item cost:10
Sorry, cheapest is 20

bisect will find the price in the list in O(log n) time, if the item at the index returns from bisect is <= we have a sale so we output the message and remove the item, if it is not then the user is cheap and cannot afford our high quality items and we show them the cheapest available.

You lso need to handle the case when a user enters either something not in our shop or something that cannot be cast to an int, a try/except and a while loop will do that for you, that I will leave as an exercise for yourself.