Question

我要做的是检查＆＃39; dragonLoot＆＃39;中的值。存在于dictionairy＆＃39; inv＆＃39;键。如果是这样，我想为该值添加1，如果不是，我想创建一个具有该值的新键并添加1.

我认为我已经获得了if，else部分正确，但我有点想让它循环并重现 TypeError：list indices必须是整数，而不是str 错误。这是代码：

#Inventory and the Loot value
inv = {'gold coin': 42, 'rope': 1}
dragonLoot = ['gold coin', 'dagger', 'gold coin', 'gold coin', 'ruby']

#Function to loop through the items in the list
def displayInventory(inventory):
    print('Inventory:')
    item_total = 0
    for j, k in inventory.items():
        print(str(k) + ' ' + j)
        item_total += k
    print('Total number of items: %s' % str(item_total))

#Where the problem occur
def addToInventory(inventory, addedItems):
    for i in addedItems:
        if addedItems[i] in inventory.keys():
            #Edit: I see an error here now, but I will fix it after I get the loop working
            inventory[addedItems[i]] + 1
        else:
            inventory.setdefault(addedItems[i], 1)

inv = addToInventory(inv, dragonLoot)
displayInventory(inv)

我已经尝试了很多我在StackOverflow上找到的其他解决方案，但没有任何诀窍。是否可能导致其他一些与Loop本身无关的错误？

完整追溯：

Traceback (most recent call last):
File "C:/Users/*****/Dropbox/*****", line 19, in   <module>
inv = addToInventory(inv, dragonLoot)
File "C:/Users/*****/Dropbox/*****", line 14, in  addToInventory
if addedItems[i] in inventory.keys():
TypeError: list indices must be integers, not str

Answer 1

为什么不使用计数器？

#Inventory and the Loot value
inv = {'gold coin': 42, 'rope': 1}
dragonLoot = ['gold coin', 'dagger', 'gold coin', 'gold coin', 'ruby']

import collections
inv = collections.Counter(inv)
inv.update(dragonLoot)

print inv

产生

Counter({'gold coin': 45, 'rope': 1, 'dagger': 1, 'ruby': 1})

有关计数器的详情，请参阅pymotw

Answer 2

我猜这个问题就在这里 -

def addToInventory(inventory, addedItems):
    for i in addedItems:
        if addedItems[i] in inventory.keys(): #<--- guessing this is the line.

问题是，当你执行for i in addedItems:时，它会循环遍历列表中的元素，而不是列表索引。所以i会是 - 'gold coin'，然后是'dagger'等项目。不是列表的索引，因此您可以将检查作为 - if i in inventory.keys():。代码 -

def addToInventory(inventory, addedItems):
    for i in addedItems:
        if i in inventory.keys():
            inventory[i] + 1
        else:
            inventory.setdefault(i, 1)

对于您的情况，要计算列表中的项目数，您可以使用 - collections.Counter

示例 -

>>> import collections
>>> dragonLoot = ['gold coin', 'dagger', 'gold coin', 'gold coin', 'ruby']
>>> invt = dict(collections.Counter(dragonLoot))
>>> invt
{'ruby': 1, 'dagger': 1, 'gold coin': 3}

Answer 3

我想有点晚了，但我正在做同样的教程。我想出的解决方案是：

def addToInventory(inventory, addedItems): for i in range(len(addedItems)): if addedItems[i] in inventory: inventory[addedItems[i]] += 1 else: inventory.setdefault(addedItems[i],1) return inventory

至少它按预期工作。希望它可以帮助别人！

Python List Loop Error：TypeError：list indices必须是整数，而不是str

3 个答案: