多线程读写文件加锁与不加锁

1、实现文件读写的文件ltz_schedule_times.py

#! /usr/bin/env python
#coding=utf-8
import os

def ReadTimes():
    res = []
    if os.path.exists('schedule_times.txt'):
        fp = open('schedule_times.txt', 'r')
    else:
        os.system('touch schedule_times.txt')
        fp = open('schedule_times.txt', 'r')
    try:
        line = fp.read()
        if line == None or len(line)==0:
            fp.close()
            return 0
        tmp = line.split()
        print 'tmp: ', tmp
        schedule_times = int(tmp[-1])
    finally:
        fp.close()
    #print schedule_times
    return schedule_times

def WriteTimes(schedule_times):
    if schedule_times <= 10:
        fp = open('schedule_times.txt', 'a+')#10以内追加进去
    else:
        fp = open('schedule_times.txt', 'w')#10以外重新写入
        schedule_times = 1
    print 'write schedule_times start!'
    try:

        fp.write(str(schedule_times)+'\n')
    finally:
        fp.close()
        print 'write schedule_times finish!'

if __name__ == '__main__':

    schedule_times = ReadTimes()
    #if schedule_times > 10:
    #    schedule_times = 0
    print schedule_times
    schedule_times = schedule_times + 1
    WriteTimes(schedule_times)

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2.1、不加锁对文件进行多线程读写。file_lock.py

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

from threading import Thread
import threading
import time
from ltz_schedule_times import *

#1、不加锁
def lock_test():
    time.sleep(0.1) 
    schedule_times = ReadTimes()
    print schedule_times
    schedule_times = schedule_times + 1
    WriteTimes(schedule_times)


if __name__ == '__main__':

    for i in range(5):
        Thread(target = lock_test, args=()).start()

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得到结果：

0
write schedule_times start!
write schedule_times finish!
tmp: tmp: tmp: tmp:     [[[['1''1''1''1']]]]



11

1
 1
write schedule_times start!write schedule_times start!

write schedule_times start!write schedule_times start!

write schedule_times finish!
write schedule_times finish!
write schedule_times finish!write schedule_times finish!

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文件写入结果：

以上结果可以看出，不加锁多线程读写文件会出现错误。

2.2、加锁对文件进行多线程读写。file_lock.py

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

from threading import Thread
import threading
import time
from ltz_schedule_times import *

#2、加锁
mu = threading.Lock() #1、创建一个锁
def lock_test():
    #time.sleep(0.1) 
    if mu.acquire(True): #2、获取锁状态，一个线程有锁时，别的线程只能在外面等着
        schedule_times = ReadTimes()
        print schedule_times
        schedule_times = schedule_times + 1
        WriteTimes(schedule_times)
        mu.release() #3、释放锁      

if __name__ == '__main__':

    for i in range(5):
        Thread(target = lock_test, args=()).start()

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结果：

0
write schedule_times start!
write schedule_times finish!
tmp:  ['1']
1
write schedule_times start!
write schedule_times finish!
tmp:  ['1', '2']
2
write schedule_times start!
write schedule_times finish!
tmp:  ['1', '2', '3']
3
write schedule_times start!
write schedule_times finish!
tmp:  ['1', '2', '3', '4']
4
write schedule_times start!
write schedule_times finish!

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文件写入结果：

达到读写效果。