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Editorial Team
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Asked: 2026-06-12T17:10:01+00:00

I have noticed that python always remembers where it finished writing in a file

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I have noticed that python always remembers where it finished writing in a file and continues from that point.
Is there a way to reset that so that if the files is edited by another program that removes certain text and ads another python will not fill the gaps with NULL when it does next write?

I have the file open in the parent and the threading children are writing to it. I used flush to ensure after write the data is physically written to the file, but that is only good to do that.

Is there another function I seem to miss that will make python append properly?

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1 Answer

  1. Editorial Team

    One safe thing, OS independent, and reliable is certainly to close the file, and open it again on writting.

    If the performance hindrance due to that is unacceptable, you could try to use “seek” to move to the end of file before writing. I just did some naive testing in the interactive console, and indeed, using file.seek(0, os.SEEK_END) before writing worked.

    Not that I think having two processes writing to the same file could be safe under most circumstances — you will end up in race conditions of some sort doing this. One way around is to implement file-locks, so that one process just write to the file after acquiring the lock. Having this done in the right wya may be thought. So, ceck if your application wpould not be in better place using something to written data carefully built and hardened along the years to allow simultanous update by various processes, like an SQL engine (MySQL or Postgresql).

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