@author jackzhenguo
@desc
@date 2019/12/3
129 groupby单字段分组
天气记录：
a = [{'date': '2019-12-15', 'weather': 'cloud'},
{'date': '2019-12-13', 'weather': 'sunny'},
{'date': '2019-12-14', 'weather': 'cloud'}]
按照天气字段weather分组汇总：
from itertools import groupby
for k, items in groupby(a,key=lambda x:x['weather']):
print(k)
输出结果看出，分组失败！原因：分组前必须按照分组字段排序，这个很坑~
cloud
sunny
cloud
修改代码：
a.sort(key=lambda x: x['weather'])
for k, items in groupby(a,key=lambda x:x['weather']):
print(k)
for i in items:
print(i)
输出结果：
cloud
{'date': '2019-12-15', 'weather': 'cloud'}
{'date': '2019-12-14', 'weather': 'cloud'}
sunny
{'date': '2019-12-13', 'weather': 'sunny'}
