如何退出Python多重處理循環？

Question

我有一個多處理代碼，用於在特定情況下搜索數據庫記錄，當它到達數據庫的末尾時，循環必須停止，我該怎麼做？這裏是代碼：

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

將您的查詢/光標移動爲可迭代，讓多處理爲您分配工作。

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()