[Python-ideas] BackupFile

Christian Heimes lists at cheimes.de
Mon Jun 25 15:59:40 CEST 2012

Am 25.06.2012 14:17, schrieb Kim Gräsman:
> Hello,
> I'm new here, so forgive me if this has been discussed before or is off-topic.
> I came up with a mechanism that I thought might be useful in the
> Python standard library -- a scope-bound self-restoring backup file. I
> came to this naïve implementation;

Are you aiming for atomic file rollover backed by a temporary file?
That's the common way to safely overwrite an existing file. It works
differently than your code.

* Create a temporary file with O_CREAT | O_EXCL in the same directory as
the file you like to replace

* Write data to new file

* Call sync() on the file as well as fdatasync() and fsync() on the file

* close the file

* use atomic rename to replace the old file with the new file (IIRC
won't work atomically on Windows)

I've some code laying around somewhere that implements a RolloverFile
similar to tempfile.NamedTemporaryFile.


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