如何在python中按年份对行对象列表进行分组？

Question

我有一个课程，例如：

class Row(object):
    def __init__(self, res_json):
        test = res_json['test']
        value = res_json['value']
        year = res_json['date'][0:4]

如果我有一个行对象列表，并且想按年份对它们进行分组，那么最好的方法是什么？

Answer 1

使用itertools.groupby：

from itertools import groupby
from operator import attrgetter

rows = []  # list of row objects

for year, group in groupby(rows, key=attrgetter('year')):
    # do stuff with the year and the group here