python - 对 python 列表中的相关值求和

Question

这是从记录中打印的值，我需要根据第二个数字对第一个数字求和。如果第一个第二个数字相同，则需要添加第一个数字。

record = [[2, 3], [3, 3], [5, 4], [1, 4]]

Expected output = [5, 3], [6, 4]]

Answer 1

您应该先排序，然后 itertools.groupby 第二个值。

import itertools
import operator

records = [[2, 3], [3, 3], [5, 4], [1, 4]]
records.sort(key=operator.itemgetter(1))
groups = itertools.groupby(records, key=operator.itemgetter(1))
# groups is now a generator that produces the values:
#   (3, [[2, 3], [3, 3]])
#   (4, [[5, 4], [1, 4]])

然后生成一个结果列表:

result = [[sum(record[0] for record in records), grpname] for grpname, records in groups]