如何退出Python多重处理循环？

Question

我有一个多处理代码，用于在特定情况下搜索数据库记录，当它到达数据库的末尾时，循环必须停止，我该怎么做？这里是代码：

import psycopg2 
from multiprocessing import Pool 

conn = psycopg2.connect(a database) 
query=conn.cursor() 
query.execute(some query) 

def scanfile(): 
    try: row=query.fetchone() 
    except: return False #here the loop must stop 
    #do something with row... 

if __name__=='__main__': 
    pool=Pool() 
    while True: 
     pool.apply_async(scanfile) 
    pool.close() 
    pool.join() 

Answer 1

将您的查询/光标移动为可迭代，让多处理为您分配工作。

import psycopg2 
from multiprocessing import Pool 


def scanfile(row): 
    #do something with row... 


if __name__ == '__main__': 
    conn = psycopg2.connect(a database) 
    query = conn.cursor() 
    query.execute(some query) 
    pool = Pool() 
    pool.map_async(scanfile, query).wait() 
    pool.close() 
    pool.join()