python - 检查字典中的唯一值并返回列表

Question

我已经为这个练习苦苦挣扎了几天，我找到的每个近似值都有一个新问题，我的想法是在字典中找到那些唯一的值，并返回一个包含键的列表

例如:如果 aDictionary = {1: 1, 3: 2, 6: 0, 7: 0, 8: 4, 10: 0} 那么你的函数应该返回 [1, 3, 8 ]，因为值 1,2 和 4 只出现一次。

这是我到目前为止尝试过的:

def existsOnce(aDict):

counting = {}
tempList = []

for k in aDict.keys():
    print k,
    print aDict[k]


print 'values are:'
for v in aDict.values():
    print v,
    counting[v] = counting.get(v,0)+1
    print counting[v]
    tempNumbers = counting[v]
    tempList.append(tempNumbers)
print tempList

如果我这样做，我可以指向并删除大于 1 的那些，但问题仍然存在，我将有一个零，我不想要它，因为它在原始列表中不是唯一的。

def existsOnce2(aDict):

# import Counter module in the top with `from collections import Counter`

c = Counter()

for letter in 'here is a sample of english text':
    c[letter] += 1
    if c[letter] == 1:
        print c[letter],':',letter

我尝试用这种方式处理整数并检查哪些是第一次出现的，但无法将其翻译成字典或从这里继续。另外我不确定答案中是否允许导入模块，并且肯定必须是一种没有外部模块的方法。

def existsOnce3(aDict):

    vals = {}
    for i in aDict.values():
        for j in set(str(i)):
            vals[j] = 1+ vals.get(j,0)
    print vals

    '''till here I get a counter of how many times a value appears in the original dictionary, now I should delete those bigger than 1'''
    temp_vals = vals.copy()
    for x in vals:
        if vals[x] > 1:
            print 'delete this: ', 'key:',x,'value:', vals[x]
            temp_vals.pop(x)
        else:
            pass
    print 'temporary dictionary values:', temp_vals
    '''till here I reduced down the values that appear once, 1, 2 and 4, now I would need the go back and check the original dictionary and return the keys
        Original dictionary: {1: 1, 3: 2, 6: 0, 7: 0, 8: 4, 10: 0}
        temp_vals {'1': 1, '2': 1, '4': 1}
        keys on temp_vals (1,2,4) are the values associated to the keys I got to retrieve from original dictionary (1,3,8)
    '''
    print '---'

    temp_list = []
    for eachTempVal in temp_vals:
        temp_list.append(eachTempVal)
    print 'temporary list values:', temp_list
    ''' till here I got a temporary list with the values I need to search in aDict'''
    print '---'
    for eachListVal in temp_list:
        print 'eachListVal:', eachListVal
        for k,v in aDict.iteritems():
            print 'key:',k,'value:',v

从这里我无法出于任何原因获取值并比较它们，我尝试使用如下语句提取值:

if v == eachListVal:
    do something

但我做错了，无法访问这些值。

Answer 1

您只需要使用您的 vals 字典，并保留来自 aDict 的键，其值在 vals 中具有 count == 1 然后调用排序以获得排序的输出列表:

def existsOnce3(aDict):  
    vals = {}
    # create dict to sum all value counts
    for i in aDict.values():
        vals.setdefault(i,0)
        vals[i] += 1   
    # use each v/val from aDict as the key to vals
    # keeping each k/key from aDict if the count is 1
    return sorted(k for k, v in aDict.items() if vals[v] == 1)

使用 collections.Counter dict 进行计数，只需对您的值调用 Counter，然后应用相同的逻辑，只需保留来自 Counter dict 的每个具有 v count == 1 的 k:

from collections import Counter
cn = Counter(aDict.values())
print(sorted(k for k,v in aDict.items() if cn[v] == 1))