如何退出Python多处理循环？

Question

我有一个多处理代码，用于搜索数据库记录中的特定条件，当到达数据库末尾时，循环必须停止，该怎么办？ 这是代码：

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/光标移到可迭代的位置，并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()