Python-分组并求和一个元组列表

>>> [(x[0:2] + (sum(z[2] for z in y),) + x[2:5]) for (x, y) in      itertools.groupby(sorted(L, key=operator.itemgetter(0, 1, 3, 4)),      key=operator.itemgetter(0, 1, 3, 4))][  ('A', '', Decimal('21.0000000000'), 1330, datetime.datetime(2012, 5, 14, 0, 0)),  ('A', '', Decimal('4.0000000000'), 1330, datetime.datetime(2012, 6, 8, 0, 0)),  ('AA', 'C', Decimal('31.0000000000'), 1330, datetime.datetime(2012, 5, 31, 0, 0)),  ('B', '', Decimal('7.0000000000'), 1330, datetime.datetime(2012, 5, 24, 0, 0)),  ('B', '', Decimal('31.0000000000'), 1330, datetime.datetime(2012, 6, 4, 0, 0))]

（注意：重新格式化输出）