python 之多線程編程

今天，看了python 核心編程的第四章，多線程編程，記錄一下要點。 1、進程和線程 進程是一個執行中的程式，每個進程都有自己的地址空間、記憶體、資料棧以及其他用於跟蹤執行的輔助資料.。 線程，實在同一個進程下執行的，共用相同的上下文，一個進程中的各個線程與主線程共用一片資料空間，線程之間的資訊共用和通訊會更加容易。 2、使用多線程 python 中有thread 模組和 threading 模組

thread模組的核心函數是thread.start_new_thread(),使用thread模組的案例.

import threadfrom time import ctime, sleeploops = [4,2]def loop(nloop, nsec, lock):print 'start loop', nloop, 'at:', ctime()sleep(nsec)print 'loop', nloop, 'done at:' , ctime()lock.release()def main():print 'starting at:', ctime()locks = []nloops = range(len(loops))for i in nloops:lock = thread.allocate_lock()lock.acquire()locks.append(lock)for i in nloops:thread.start_new_thread(loop,(i, loops[i], locks[i]))for i in nloops:while locks[i].locked():passprint 'all Done at: ', ctime()if __name__ == '__main__':main()

threading 模組 threadIng模組與thread模組相比，它支援守護線程。守護線程的概念可以這樣理解，如果一個線程設定為守護線程，就表示這個線程是不重要的，進程退出時不需要等待這個線程執行完成。 如果要將一個線程設定為守護線程，需要線上程執行之前，設定 thread.daemon = True 使用Thread 類建立多線程案例，

import threadingfrom time import sleep, ctimeclass MyThread(threading.Thread):"""docstring for MyThread"""def __init__(self, func, args, name=''):super(MyThread, self).__init__()self.name = nameself.func = funcself.args = argsdef getResult(self):return self.resdef run(self):self.res = self.func(*self.args)loops = [4,2]def loop(nloop, nsec):print 'start loop', nloop, 'at: ', ctime()sleep(nsec)print 'loop done', nloop, 'at: ', ctime()return 'ws'def main():print 'starting at: ', ctime()threads = []nloops = range(len(loops))for i in nloops:#t = threading.Thread(target = loop, args = (i, loops[i]))t = MyThread(loop,(i,loops[i]),loop.__name__)threads.append(t)for i in nloops:threads[i].start()for i in nloops:threads[i].join()print threads[i].getResult()if __name__ == '__main__':main()

3、同步原語 使用同步的情況，在使用多線程時，有些特定的函數或者代碼塊不希望被多個線程同時執行。

#!/usr/bin/env pythonfrom atexit import registerfrom random import randrangefrom threading import Thread, Lock, currentThreadfrom time import sleep, ctimeclass CleanOutputSet(set):    def __str__(self):        return ', '.join(x for x in self)lock = Lock()loops = (randrange(2, 5) for x in xrange(randrange(3, 7)))remaining = CleanOutputSet()def loop(nsec):    myname = currentThread().name    lock.acquire()    remaining.add(myname)    print '[%s] Started %s' % (ctime(), myname) #print '[{0}] Started {1}'.format(ctime(), myname)    lock.release()    sleep(nsec)    lock.acquire()    remaining.remove(myname)    print '[%s] Completed %s (%d secs)' % ( #print '[{0}] Completed {1} ({2} secs)'.format(        ctime(), myname, nsec)    print '    (remaining: %s)' % (remaining or 'NONE') #print '    (remaining: {0})'.format(remaining or 'NONE')    lock.release()def _main():    for pause in loops:        Thread(target=loop, args=(pause,)).start()@registerdef _atexit():    print 'all DONE at:', ctime()if __name__ == '__main__':    _main()

python支援的多種類型的同步原語，包括鎖/互斥、訊號量 使用鎖時，調用lock.require()函數擷取鎖，調用lock.release()函數釋放鎖