列表的python sum和merge元素

Question

我有一些类似的列表

[ ['2000-01-01', 1.0], ['2000-02-01', 2.0] ]
[ ['2000-01-01', 2.0], ['2000-02-01', 1.0], ['2000-03-01', 3.0] ]
[ ['2000-01-01', 3.1], ['2000-02-01', 2.0], ['2000-03-01', 1.4] ]

我如何合并数据时间并求和值得到这样的列表

[ ['2000-01-01', 6.1], ['2000-02-01', 5.0], ['2000-03-01', 4.4] ]

列表中元素的类型为[datetime，double]

Answer 1

在此处使用collections.defaultdict()。请参阅片段。

>>> a = [ ['2000-01-01', 1.0], ['2000-02-01', 2.0] ]
>>> b = [ ['2000-01-01', 2.0], ['2000-02-01', 1.0], ['2000-03-01', 3.0] ]
>>> c = [ ['2000-01-01', 3.0], ['2000-02-01', 2.0], ['2000-03-01', 1.0] ]
>>> from collections import defaultdict
>>> m = defaultdict(int)
>>> d = a + b + c
>>> d
[['2000-01-01', 1.0], ['2000-02-01', 2.0], ['2000-01-01', 2.0], ['2000-02-01', 1.0], ['2000-03-01', 3.0], ['2000-01-01', 3.0], ['2000-02-01', 2.0], ['2000-03-01', 1.0]]
>>> for date, count in d:
        m[date] += count
>>> m.items()
[('2000-02-01', 5.0), ('2000-03-01', 4.0), ('2000-01-01', 6.0)]

Answer 2

对于所有类似Excel的编程，我建议使用Pandas。但是，如果您想继续使用标准lib，Counter就足够了。

Answer 3

使用计数器。计数器：

from collections import Counter
result = Counter()
result += Counter(dict([ ['2000-01-01', 1], ['2000-02-01', 2] ]))
result += Counter(dict([ ['2000-01-01', 2], ['2000-02-01', 1], ['2000-03-01', 3] ]))
result += Counter(dict([ ['2000-01-01', 3], ['2000-02-01', 2], ['2000-03-01', 1] ]))
result.most_common() # => [('2000-01-01', 6), ('2000-02-01', 5), ('2000-03-01', 4)]

Answer 4

使用计数器

#inputList is List containg 
from collections import Counter
from operator import itemgetter
def mergeAndGetSum(inputList):
    cnt = Counter()
    #get counts for each date
    for list1 in inputList:
        for list2 in list1:
            cnt[list2[0]] += list2[1]
    ret = []
    #creaet the output list
    for key in cnt:
        ret.append([key,cnt[key]])
    #sort output list based on dates
    ret.sort(key=itemgetter(0))
    return ret

if __name__ == "__main__":
    listOfLists = [
            [ ['2000-01-01', 1], ['2000-02-01', 2] ],
            [ ['2000-01-01', 2], ['2000-02-01', 1], ['2000-03-01', 3] ],
            [ ['2000-01-01', 3], ['2000-02-01', 2], ['2000-03-01', 1] ]
            ]
    ret = mergeAndGetSum(listOfLists)
    print ret