在Python中通过threading模块定义和调用线程的方法

定义线程

最简单的方法：使用target指定线程要执行的目标函数，再使用start()启动。

语法：

    class threading.Thread(group=None, target=None, name=None, args=(), kwargs={})

group恒为None，保留未来使用。target为要执行的函数名。name为线程名，默认为Thread-N，通常使用默认即可。但服务器端程序线程功能不同时，建议命名。

    #!/usr/bin/env python3
    # coding=utf-8
    import threading

    def function(i):
      print ("function called by thread {0}".format(i))
    threads = []

    for i in range(5):
      t = threading.Thread(target=function , args=(i,))
      threads.append(t)
      t.start()
      t.join()

执行结果：

    $ ./threading_define.py 

    function called by thread 0
    function called by thread 1
    function called by thread 2
    function called by thread 3
    function called by thread 4

确定当前线程

    #!/usr/bin/env python3
    # coding=utf-8

    import threading
    import time

    def first_function():
      print (threading.currentThread().getName()+ str(' is Starting \n'))
      time.sleep(3)
      print (threading.currentThread().getName()+ str( ' is Exiting \n'))

    def second_function():
      print (threading.currentThread().getName()+ str(' is Starting \n'))
      time.sleep(2)
      print (threading.currentThread().getName()+ str( ' is Exiting \n'))

    def third_function():
      print (threading.currentThread().getName()+\
      str(' is Starting \n'))
      time.sleep(1)
      print (threading.currentThread().getName()+ str( ' is Exiting \n'))

    if __name__ == "__main__":
      t1 = threading.Thread(name='first_function', target=first_function)
      t2 = threading.Thread(name='second_function', target=second_function)
      t3 = threading.Thread(name='third_function',target=third_function)
      t1.start()
      t2.start()
      t3.start()

执行结果：

    $ ./threading_name.py 

    first_function is Starting 
    second_function is Starting 
    third_function is Starting 
    third_function is Exiting 
    second_function is Exiting 
    first_function is Exiting

配合logging模块一起使用：

    #!/usr/bin/env python3
    # coding=utf-8

    import logging
    import threading
    import time

    logging.basicConfig(
      level=logging.DEBUG,
      format='[%(levelname)s] (%(threadName)-10s) %(message)s',
      )

    def worker():
      logging.debug('Starting')
      time.sleep(2)
      logging.debug('Exiting')

    def my_service():
      logging.debug('Starting')
      time.sleep(3)
      logging.debug('Exiting')

    t = threading.Thread(name='my_service', target=my_service)
    w = threading.Thread(name='worker', target=worker)
    w2 = threading.Thread(target=worker) # use default name
    w.start()
    w2.start()
    t.start()

执行结果：

    $ ./threading_names_log.py[DEBUG] (worker  ) Starting

    [DEBUG] (Thread-1 ) Starting
    [DEBUG] (my_service) Starting
    [DEBUG] (worker  ) Exiting
    [DEBUG] (Thread-1 ) Exiting
    [DEBUG] (my_service) Exiting

在子类中使用线程

前面我们的线程都是结构化编程的形式来创建。通过集成threading.Thread类也可以创建线程。Thread类首先完成一些基本上初始化，然后调用它的run()。run()方法会会调用传递给构造函数的目标函数。

    #!/usr/bin/env python3
    # coding=utf-8

    import logging
    import threading
    import time

    exitFlag = 0

    class myThread (threading.Thread):
      def __init__(self, threadID, name, counter):
        threading.Thread.__init__(self)
        self.threadID = threadID
        self.name = name
        self.counter = counter

      def run(self):
        print ("Starting " + self.name)
        print_time(self.name, self.counter, 5)
        print ("Exiting " + self.name)

    def print_time(threadName, delay, counter):
      while counter:
        if exitFlag:
          thread.exit()
        time.sleep(delay)
        print ("%s: %s" %(threadName, time.ctime(time.time())))
        counter -= 1

    # Create new threads
    thread1 = myThread(1, "Thread-1", 1)
    thread2 = myThread(2, "Thread-2", 2)
    # Start new Threads
    thread1.start()
    thread2.start()
    print ("Exiting Main Thread")

执行结果：

    $ ./threading_subclass.py 

    Starting Thread-1
    Starting Thread-2
    Exiting Main Thread
    Thread-1: Tue Sep 15 11:03:21 2015
    Thread-2: Tue Sep 15 11:03:22 2015
    Thread-1: Tue Sep 15 11:03:22 2015
    Thread-1: Tue Sep 15 11:03:23 2015
    Thread-2: Tue Sep 15 11:03:24 2015
    Thread-1: Tue Sep 15 11:03:24 2015
    Thread-1: Tue Sep 15 11:03:25 2015
    Exiting Thread-1
    Thread-2: Tue Sep 15 11:03:26 2015
    Thread-2: Tue Sep 15 11:03:28 2015
    Thread-2: Tue Sep 15 11:03:30 2015
    Exiting Thread-2