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Groups > comp.lang.python > #25228

Re: How to safely maintain a status file

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>> This is not a contradiction. Although the rename operation is atomic,
>> the whole "change status" process is not. It is because there are two
>> operations: #1 delete old status file and #2. rename the new status
>> file. And because there are two operations, there is still a race
>> condition. I see no contradiction here.
> On Posix systems, you can avoid the race condition.  The trick is to
> skip step #1.  The rename will implicitly delete the old file, and
> it will still be atomic.  The whole process now consists of a single
> stop, so the whole process is now atomic.
Well, I didn't know that this is going to work. At least it does not 
work on Windows 7 (which should be POSIX compatible?)

 >>> f = open("test.txt","wb+")
 >>> f.close()
 >>> f2 = open("test2.txt","wb+")
 >>> f2.close()
 >>> import os
 >>> os.rename("test2.txt","test.txt")
Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
WindowsError: [Error 183] File already exists
 >>>

I have also tried this on FreeBSD and it worked.

Now, let's go back to the original question:

>>>This works well on Linux but Windows raises an error when status_file already exists.

It SEEMS that the op wanted a solution for Windows....

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Re: How to safely maintain a status file Laszlo Nagy <gandalf@shopzeus.com> - 2012-07-12 14:30 +0200
  Re: How to safely maintain a status file Hans Mulder <hansmu@xs4all.nl> - 2012-07-12 15:19 +0200
    Re: How to safely maintain a status file Laszlo Nagy <gandalf@shopzeus.com> - 2012-07-12 19:43 +0200
    Re: How to safely maintain a status file Christian Heimes <lists@cheimes.de> - 2012-07-12 20:39 +0200
      Re: How to safely maintain a status file Rick Johnson <rantingrickjohnson@gmail.com> - 2012-07-12 18:20 -0700
        Re: How to safely maintain a status file Chris Angelico <rosuav@gmail.com> - 2012-07-13 12:12 +1000
          Re: How to safely maintain a status file Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-13 03:13 +0000
            Re: How to safely maintain a status file Gene Heskett <gheskett@wdtv.com> - 2012-07-12 23:49 -0400
              Re: How to safely maintain a status file Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-13 04:21 +0000
            Re: How to safely maintain a status file rantingrickjohnson@gmail.com - 2012-07-12 21:26 -0700
              Re: How to safely maintain a status file Chris Angelico <rosuav@gmail.com> - 2012-07-13 16:02 +1000
              Re: How to safely maintain a status file Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-13 07:14 +0000
                Re: How to safely maintain a status file Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-07-13 13:29 -0400
              RE: How to safely maintain a status file "Prasad, Ramit" <ramit.prasad@jpmorgan.com> - 2012-07-13 16:00 +0000
              Re: [Python] RE: How to safely maintain a status file Chris Gonnerman <chris@gonnerman.org> - 2012-07-13 12:27 -0500
              RE: [Python] RE: How to safely maintain a status file "Prasad, Ramit" <ramit.prasad@jpmorgan.com> - 2012-07-13 17:59 +0000
                Re: [Python] RE: How to safely maintain a status file Hans Mulder <hansmu@xs4all.nl> - 2012-07-13 20:28 +0200
                Re: [Python] RE: How to safely maintain a status file MRAB <python@mrabarnett.plus.com> - 2012-07-13 20:57 +0100
                Re: [Python] RE: How to safely maintain a status file Christian Heimes <lists@cheimes.de> - 2012-07-13 22:21 +0200
              Re: [Python] RE: How to safely maintain a status file Chris Angelico <rosuav@gmail.com> - 2012-07-14 04:19 +1000
              RE: How to safely maintain a status file Chris Gonnerman <chris@gonnerman.org> - 2012-07-13 15:15 -0500
                Re: How to safely maintain a status file Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-14 01:53 +0000

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