TypeError:“dict_items”对象在运行if语句时不可订阅到短列表项

Question

我使用下面的一个函数来运行apriori算法并计算所有项集的支持度、置信度。该函数使用dictionary对象来存储项目的所有值及其相应的支持度、置信度。在

在运行if语句选择支持值最小值为0.15、置信度为0.6的项之后，在dict_items对象不可订阅的下面，我得到了一个错误。在

for key, value in largeSet.items()[1:]:

TypeError: 'dict_items' object is not subscriptable



def runApriori(data_iter, minSupport, minConfidence):
    """
    run the apriori algorithm. data_iter is a record iterator
    Return both:
     - items (tuple, support)
     - rules ((pretuple, posttuple), confidence)
    """
    itemSet, transactionList = getItemSetTransactionList(data_iter)

    freqSet = defaultdict(int)
    largeSet = dict()
    # Global dictionary which stores (key=n-itemSets,value=support)
    # which satisfy minSupport

    assocRules = dict()
    # Dictionary which stores Association Rules

    oneCSet = returnItemsWithMinSupport(itemSet,
                                        transactionList,
                                        minSupport,
                                        freqSet)

    currentLSet = oneCSet
    k = 2
    while(currentLSet != set([])):
        largeSet[k-1] = currentLSet
        currentLSet = joinSet(currentLSet, k)
        currentCSet = returnItemsWithMinSupport(currentLSet,
                                                transactionList,
                                                minSupport,
                                                freqSet)
        currentLSet = currentCSet
        k = k + 1

    def getSupport(item):
            """local function which Returns the support of an item"""
            return float(freqSet[item])/len(transactionList)

    toRetItems = []
    for key, value in largeSet.items():
        toRetItems.extend([(tuple(item), getSupport(item))
                           for item in value])

    toRetRules = []
    for key, value in largeSet.items()[1:]:
        for item in value:
            _subsets = map(frozenset, [x for x in subsets(item)])
            for element in _subsets:
                remain = item.difference(element)
                if len(remain) > 0:
                    confidence = getSupport(item)/getSupport(element)
                    if confidence >= minConfidence:
                        toRetRules.append(((tuple(element), tuple(remain)),
                                           confidence))
    return toRetItems, toRetRules

if __name__ == "__main__":
    inFile = ''
    minSupport = 0.15
    minConfidence = 0.6

    items, rules = runApriori(inFile, minSupport, minConfidence)

    printResults(items, rules) 

Answer 1

在cpython3.6之前（对于任何Python解释器，dicts没有可靠的顺序，所以假设第一个项目是您想要跳过的项目是一个不好的想法。在

也就是说，如果您使用的是3.6+、和您知道要跳过第一个元素，可以use ^{}安全地执行此操作，更改：

for key, value in largeSet.items()[1:]:

收件人：

^{pr2}$

Answer 2

你不应该依赖字典有特定的顺序，所以python不允许你跳过字典中的“第一个”项，因为“第一个”取决于有一个特定的顺序。您可以将其强制转换为一个列表：for key, value in list(largeSet.items())[1:]，但这取决于字典的顺序是您所期望的。最好只执行for key, value in largeSet.items())，然后在循环中检查它是否是您不想操作的项，如果是，continue。或者用熊猫系列。在