day40-python多进程多线程-多线程实例和锁

多线程

线程是应用程序中工作的最小单元。

多线程是现实有两种方式：
方法一：将要执行的方法作为参数传给Thread的构造方法（和多进程类似）
t = threading.Thread(target=action, args=(i,))

方法二：从Thread继承，并重写run()

所以如果重写了run，就直接调用run的函数了，如果run没有重新，就调用target函数。

实例

import threading

方法一
def worker(n):
    print("start worker{0}".format(n))

方法二
class Mythread(threading.Thread):
    def __init__(self,args):
        super(Mythread,self).__init__()
        self.args = args
    def run(self):
        print("start MyThread{0}".format(self.args))

if __name__ == "__main__":
    for i in xrange(1,6):

        t1 = threading.Thread(target=worker,args=(i,))
        t1.start()
    t1.join()
    for x in xrange(6,11):
        t2 = Mythread(x)
        t2.start()
    t2.join()

输出结果：
start worker1
start worker2
start worker3
start worker4
start worker5
start MyThread6
start MyThread7
start MyThread8
start MyThread9
start MyThread10

线程锁

通过threading.Lock()来创建锁，函数在执行的只有先要获得锁，左后执行完以后要释放锁：
with lock：
lock.acquire()
lock.release()

import threading
import time

def worker(name,lock):
    with lock:
        print("start {0}".format(name))
        time.sleep(5)
        print("end {0}".format(name))

if __name__ == "__main__":
    lock = threading.Lock()
    t1 = threading.Thread(target=worker, args=("worker1", lock))
    t2 = threading.Thread(target=worker, args=("worker2", lock))
    t1.start()
    t2.start()
    print("main end.")

输出结果
start worker1
main end.
end worker1   #中间间隔5秒
start worker2
end worker2