引言
在Python中编写多进程间共同读写文件的过程中，需要对文件句柄进行互斥操作，否则造成文件读写混乱或者损坏。在Posix环境下（Linux/Unix）下，可以直接调用fcntl模块进行控制，Windows平台没有该模块，只能通过安装 pywin 模块，调用系统的 API进行互斥操作了。
实现代码
#!/usr/bin/env python
#-*- coding: utf-8 -*-
#@author : Thomas Hu
#@date : 2015-03-23
#@version : 1.0
import os
import multiprocessing
if os.name == 'nt':
import win32con, win32file, pywintypes
LOCK_EX = win32con.LOCKFILE_EXCLUSIVE_LOCK
LOCK_SH = 0 # The default value
LOCK_NB = win32con.LOCKFILE_FAIL_IMMEDIATELY
__overlapped = pywintypes.OVERLAPPED( )
def lock(file, flags):
hfile = win32file._get_osfhandle(file.fileno( ))
win32file.LockFileEx(hfile, flags, 0, 0xffff0000, __overlapped)
def unlock(file):
hfile = win32file._get_osfhandle(file.fileno( ))
win32file.UnlockFileEx(hfile, 0, 0xffff0000, __overlapped)
elif os.name == 'posix':
from fcntl import LOCK_EX, LOCK_SH, LOCK_NB
def lock(file, flags):
fcntl.flock(file.fileno( ), flags)
def unlock(file):
fcntl.flock(file.fileno( ), fcntl.LOCK_UN)
else:
raise RuntimeError("File Locker only support NT and Posix platforms!")
def writeLogfile(args):
try:
logfile, msg = args
f = open(logfile, "a+")
lock(f, LOCK_EX)
f.write(msg + "\n")
unlock(f)
except Exception as ex:
print("Error Info: %s"%(str(ex)))
finally:
f.close()
def multiExecute(logfile, count):
pool = multiprocessing.Pool(processes = count)
pool.map(writeLogfile, [(logfile, a * 80) for a in "abcdefghijk"])
if __name__ == "__main__":
logfile = "test.txt"
multiExecute(logfile, 5)
执行结果
# first time aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc dddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff gggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii jjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjj kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk # second time aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc dddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb gggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggggg hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii jjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjj kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk
注：每次的执行结果都不太一样，但是，加了文件锁后，可以保证所有的行数都会写入文件中。如果把 lock 和 unlock 所在的代码行去掉，文件中的内容就会出现丢失。