python 在threading中如何處理主進(jìn)程和子線程的關(guān)系
之前用python的多線程,總是處理不好進(jìn)程和線程之間的關(guān)系。后來(lái)發(fā)現(xiàn)了join和setDaemon函數(shù),才終于弄明白。下面總結(jié)一下。
1.使用join函數(shù)后,主進(jìn)程會(huì)在調(diào)用join的地方等待子線程結(jié)束,然后才接著往下執(zhí)行。
join使用實(shí)例如下:
import timeimport randomimport threading class worker(threading.Thread): def __init__(self): threading.Thread.__init__(self) def run(self): t = random.randint(1,10) time.sleep(t) print 'This is ' + self.getName() + ';I sleep %d second.'%(t) tsk = []for i in xrange(0,5): time.sleep(0.1) thread = worker() thread.start() tsk.append(thread)for tt in tsk: tt.join()print 'This is the end of main thread.'
運(yùn)行結(jié)果如下:
# python testjoin.py This is Thread-3;I sleep 2 second.This is Thread-1;I sleep 4 second.This is Thread-2;I sleep 7 second.This is Thread-4;I sleep 7 second.This is Thread-5;I sleep 7 second.This is the end of main thread.
這里創(chuàng)建了5個(gè)子線程,每個(gè)線程隨機(jī)等待1-10秒后打印退出;主線程分別等待5個(gè)子線程結(jié)束。最后結(jié)果是先顯示各個(gè)子線程,再顯示主進(jìn)程的結(jié)果。
2. 如果使用的setDaemon函數(shù),則與join相反,主進(jìn)程結(jié)束的時(shí)候不會(huì)等待子線程。
setDaemon函數(shù)使用實(shí)例:
import timeimport randomimport threading class worker(threading.Thread): def __init__(self): threading.Thread.__init__(self) def run(self): t = random.randint(1,10) time.sleep(t) print 'This is ' + self.getName() + ';I sleep %d second.'%(t) tsk = []for i in xrange(0,5): time.sleep(0.1) thread = worker() thread.setDaemon(True) thread.start() tsk.append(thread)print 'This is the end of main thread.'
這里設(shè)置主進(jìn)程為守護(hù)進(jìn)程,當(dāng)主進(jìn)程結(jié)束的時(shí)候,子線程被中止
運(yùn)行結(jié)果如下:
#python testsetDaemon.py This is the end of main thread.
3、如果沒(méi)有使用join和setDaemon函數(shù),則主進(jìn)程在創(chuàng)建子線程后,直接運(yùn)行后面的代碼,主程序一直掛起,直到子線程結(jié)束才能結(jié)束。
import timeimport randomimport threading class worker(threading.Thread): def __init__(self): threading.Thread.__init__(self) def run(self): t = random.randint(1,10) time.sleep(t) print 'This is ' + self.getName() + ';I sleep %d second.'%(t) tsk = []for i in xrange(0,5): time.sleep(0.1) thread = worker() thread.start() tsk.append(thread)print 'This is the end of main thread.'
運(yùn)行結(jié)果如下:
# python testthread.py This is the end of main thread.This is Thread-4;I sleep 1 second.This is Thread-3;I sleep 7 second.This is Thread-5;I sleep 7 second.This is Thread-1;I sleep 10 second.This is Thread-2;I sleep 10 second.
補(bǔ)充知識(shí):Python Thread和Process對(duì)比
原因:進(jìn)程和線程的差距(方向不同,之針對(duì)這個(gè)實(shí)例)
# coding=utf-8import loggingimport multiprocessingimport osimport timefrom threading import Threadlogging.basicConfig( level=logging.INFO, format='%(asctime)s 【 %(process)d 】 %(processName)s %(message)s')def func (i): # logging.info(f’子:{os.getpid()},t{i}’) return f’子:{os.getpid()},t{i}’def main (ctx): start01 = time.time() ts = [Thread(target=func, args=(i,)) for i in range(100)] [t.start() for t in ts] [t.join() for t in ts] end01 = time.time() - start01 logging.info(f'線程花費(fèi)的時(shí)間:{end01}秒') start02 = time.time() ps = [ctx.Process(target=func, args=(i,)) for i in range(100)] [p.start() for p in ps] [p.join() for p in ps] end02 = time.time() - start02 logging.info(f'進(jìn)程花費(fèi)的時(shí)間:{end02}秒')if __name__ == ’__main__’: # windows 啟動(dòng)方式 multiprocessing.set_start_method(’spawn’) # 獲取上下文 ctx = multiprocessing.get_context(’spawn’) # 檢查這是否是凍結(jié)的可執(zhí)行文件中的偽分支進(jìn)程。 ctx.freeze_support() main(ctx)
輸出:
2019-10-06 14:17:22,729 【 7412 】 MainProcess 線程花費(fèi)的時(shí)間:0.012967586517333984秒2019-10-06 14:17:25,671 【 7412 】 MainProcess 進(jìn)程花費(fèi)的時(shí)間:2.9418249130249023秒
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