Question

我有一个多线程函数，它都写入同一个日志文件。如何将此函数（可能带有函数装饰器）添加到日志文件中的写入执行添加到队列中。小例子：

#!/usr/bin/python

import thread
import time

# Define a function for the thread
def print_time( threadName, delay):
   count = 0
   while count < 5:
      time.sleep(delay)
      count += 1
      writeToLog(threadName, time.ctime(time.time()))
      print "%s: %s" % ( threadName, time.ctime(time.time()) )

# Create two threads as follows
try:
   thread.start_new_thread( print_time, ("Thread-1", 2, ) )
   thread.start_new_thread( print_time, ("Thread-2", 4, ) )
except:
   print "Error: unable to start thread"

def writeToLog(threadName, time):
   self.fileWriter = open("log.txt", "w")
   self.fileWriter.write("ThreadName: " + threadName + "\n")
   self.fileWriter.write("Time: " + time + "\n")
   self.fileWriter.close()

如何在执行时将此函数writeToLog添加到队列中？现在每次两个线程调用writeToLog函数都会出错，因为另一个writeToLog函数（来自另一个线程）已经关闭了文件。当这个编写器的全局变量最终关闭时，我得到如下输出：

ThreadName: thread1
ThreadName: thread2
Time: 9:50AM
Time: 9:50AM

我一直想要的输出必须如下所示：

ThreadName: Thread-1
Time: 9:50AM
ThreadName: Thread-2
Time: 9:50AM

Answer 1

对共享资源的并发访问是一个众所周知的问题。 Python线程提供了一些避免问题的机制。使用python锁：http://docs.python.org/2/library/threading.html#lock-objects 锁用于同步对共享资源的访问：

lock = Lock()

lock.acquire() # will block if lock is already held
... access shared resource
lock.release()

更多信息：http://effbot.org/zone/thread-synchronization.htm

搜索“Python同步”

为函数创建一个队列，使它在python中一次只运行一次

1 个答案: