Python的多线程有两种实现方法:
函数,线程类
1.函数
调用thread模块中的start_new_thread()函数来创建线程,以线程函数的形式告诉线程该做什么
# -*- coding: utf-8 -*- import thread def f(name): #定义线程函数 print "this is " + name if __name__ == '__main__': thread.start_new_thread(f, ("thread1",)) #用start_new_thread()调用线程函数和其他参数 while 1: pass
不过这种方法暂时没能找到其他辅助方法,连主线程等待都要用while 1这种方法解决。
2.线程类
调用threading模块,创建threading.Thread的子类来得到自定义线程类。
# -*- coding: utf-8 -*- import threading class Th(threading.Thread): def __init__(self, name): threading.Thread.__init__(self) self.t_name = name #调用父类构造函数 def run(self): #重写run()函数,线程默认从此函数开始执行 print "This is " + self.t_name if __name__ == '__main__': thread1 = Th("Thread_1") thread1.start() #start()函数启动线程,自动执行run()函数
threading.Thread类的可继承函数:
getName() 获得线程对象名称
setName() 设置线程对象名称
join() 等待调用的线程结束后再运行之后的命令
setDaemon(bool) 阻塞模式,True:父线程不等待子线程结束,False 等待,默认为False
isDaemon() 判断子线程是否和父线程一起结束,即setDaemon()设置的值
isAlive() 判断线程是否在运行
实例
import threading import time class Th(threading.Thread): def __init__(self, thread_name): threading.Thread.__init__(self) self.setName(thread_name) def run(self): print "This is thread " + self.getName() for i in range(5): time.sleep(1) print str(i) print self.getName() + "is over"
join()阻塞等待
if __name__ == '__main__': thread1 = Th("T1 ") thread1.start() #thread1.join() print "main thread is over"
不带thread1.join(),得到如下结果:
This is thread T1
main thread is over
0
1
2
T1 is over
不等待thread1完成,执行之后语句。
加了thread1.join(),得到如下结果:
This is thread T1
0
1
2
T1 is over
main thread is over
阻塞等待thread1结束,才执行下面语句
主线程等待
if __name__ == '__main__': thread1 = Th("T1 ") thread1.setDaemon(True) #要在线程执行之前就设置这个量 thread1.start() print "main thread is over"
报错:Exception in thread T1 (most likely raised during interpreter shutdown):
也就是主线程不等待子线程就结束了。
多个子线程
if __name__ == '__main__': for i in range(3): t = Th(str(i)) t.start() print "main thread is over"
这里的t可同时处理多个线程,即t为线程句柄,重新赋值不影响线程。
这里奇怪的是,运行t.run()时,不会再执行其他线程。虽不明,还是用start()吧。暂且理解为start()是非阻塞并行的,而run是阻塞的。
线程锁
threading提供线程锁,可以实现线程同步。
import threading import time class Th(threading.Thread): def __init__(self, thread_name): threading.Thread.__init__(self) self.setName(thread_name) def run(self): threadLock.acquire() #获得锁之后再运行 print "This is thread " + self.getName() for i in range(3): time.sleep(1) print str(i) print self.getName() + " is over" threadLock.release() #释放锁 if __name__ == '__main__': threadLock = threading.Lock() #设置全局锁 thread1 = Th('Thread_1') thread2 = Th('Thread_2') thread1.start() thread2.start()
得到结果:
This is thread Thread_1
0
1
2
Thread_1 is over
This is thread Thread_2
0
1
2
Thread_2 is over