Python中实现count(distinct )

假设一个表有6个字段c1,c2,c3,c4,c5,c6，有如下的sql语句:

select c1,count(distinct(c6)) from tbl where c3>1 group by c3;

Python中asq模块可以实现类似的查询，以下用一个示例说明。

#!/usr/bin/env python2.7
#-*- encoding: utf-8 -*-  

import os
from datetime import *
import time
from asq.initiators import query  

def test1():
        src_list = [[6,6,6,3,7,9],[3,1,1,45,6,34],[2,9,5,435,56,34],[8,6,8,23,4,32],[2,6,8,435,2,8],[1,3,6,432,5,22],[1,3,5,6,2,435],[2,4,6,34,2,12]]  

        res_list = query(src_list).where(lambda p: p[2]>1).group_by(lambda p:p[2]).select(lambda p:[p[0][0],p.distinct(lambda p: p[5]).count()]).to_list()  

        print res_list  

if __name__ == '__main__':  

     test1()  

 

运行结果:

[[6, 3], [2, 2], [8, 2]]
[Finished in 0.1s]

asq函数的逻辑顺序依次是: where-->group by --> select --> distinct -->返回结果列表。