分组函数（groupby、itemgetter）

from itertools import groupby
from operator import itemgetter

d1={‘name‘:‘liuyi‘,‘age‘:25,‘city‘:‘SZ‘}
d2={‘name‘:‘chener‘,‘age‘:18,‘city‘:‘SH‘}
d3={‘name‘:‘zhangsan‘,‘age‘:23,‘city‘:‘GZ‘}
d4={‘name‘:‘lisi‘,‘age‘:24,‘city‘:‘HZ‘}
d5={‘name‘:‘wangwu‘,‘age‘:22,‘city‘:‘BJ‘}
d6={‘name‘:‘zhangliu‘,‘age‘:21,‘city‘:‘WH‘}
lis = [d1,d2,d3,d4,d5,d6]

lis.sort(key=itemgetter(‘city‘))        # 使用groupby需要先排序

lst_grou = groupby(lis,itemgetter(‘city‘))  # itemgetter(‘city‘) 相当于 key = lambda x:x[‘city‘]
for key,group in lst_grou:                  # group 使一个迭代器，包含了所有的分组
    for g in group:
        print(key,g)
        
‘‘‘
结果
BJ {‘name‘: ‘wangwu‘, ‘age‘: 22, ‘city‘: ‘BJ‘}
GZ {‘name‘: ‘zhangsan‘, ‘age‘: 23, ‘city‘: ‘GZ‘}
HZ {‘name‘: ‘lisi‘, ‘age‘: 24, ‘city‘: ‘HZ‘}
SH {‘name‘: ‘chener‘, ‘age‘: 18, ‘city‘: ‘SH‘}
SZ {‘name‘: ‘liuyi‘, ‘age‘: 25, ‘city‘: ‘SZ‘}
WH {‘name‘: ‘zhangliu‘, ‘age‘: 21, ‘city‘: ‘WH‘}
‘‘‘

from itertools import groupby
from operator import itemgetter

d1={‘name‘:‘liuyi‘,‘age‘:25,‘city‘:‘SZ‘}
d2={‘name‘:‘chener‘,‘age‘:18,‘city‘:‘SH‘}
d3={‘name‘:‘zhangsan‘,‘age‘:23,‘city‘:‘GZ‘}
d4={‘name‘:‘lisi‘,‘age‘:24,‘city‘:‘SZ‘}
d5={‘name‘:‘wangwu‘,‘age‘:22,‘city‘:‘BJ‘}
d6={‘name‘:‘zhangliu‘,‘age‘:21,‘city‘:‘WH‘}
lis = [d1,d2,d3,d4,d5,d6]

lis.sort(key=itemgetter(‘city‘))        # 使用groupby需要先排序

lst_grou = groupby(lis,itemgetter(‘city‘))  # itemgetter(‘city‘) 相当于 key = lambda x:x[‘city]
print([key for key,group in lst_grou])      # 列表推导式，会自动去重

‘‘‘
结果
[‘BJ‘, ‘GZ‘, ‘SH‘, ‘SZ‘, ‘WH‘]
‘‘‘

print(dict([(key,list(group)) for key,group in lst_grou]))  # 获取字典

‘‘‘
结果
{‘BJ‘: [{‘name‘: ‘wangwu‘, ‘age‘: 22, ‘city‘: ‘BJ‘}], 
‘GZ‘: [{‘name‘: ‘zhangsan‘, ‘age‘: 23, ‘city‘: ‘GZ‘}], 
‘SH‘: [{‘name‘: ‘chener‘, ‘age‘: 18, ‘city‘: ‘SH‘}], 
‘SZ‘: [{‘name‘: ‘liuyi‘, ‘age‘: 25, ‘city‘: ‘SZ‘}, {‘name‘: ‘lisi‘, ‘age‘: 24, ‘city‘: ‘SZ‘}], 
‘WH‘: [{‘name‘: ‘zhangliu‘, ‘age‘: 21, ‘city‘: ‘WH‘}]}
‘‘‘