[Python-ideas] [Python-Dev] Ext4 data loss
steve at pearwood.info
Fri Mar 13 02:18:55 CET 2009
On Thu, 12 Mar 2009 12:26:40 pm zooko wrote:
> > Would there be interest in a filetools module? Replies and
> > discussion to python-ideas please.
> I've been using and maintaining a few filesystem hacks for, let's
> see, almost nine years now:
> (The first version of that was probably written by Greg Smith in
> about 1999.)
> I'm sure there are many other such packages. A couple of quick
> searches of pypi turned up these two:
> I wonder if any of them have the sort of functionality you're
> thinking of.
Close, but not quite.
I'm suggesting a module with a collection of subclasses of file that
exhibit modified behaviour. For example:
def write(self, data):
# similarly for writelines
plus functions which implement common idioms for safely writing data,
making backups on a save, etc. A common idiom for safely over-writing a
file while minimising the window of opportunity for file loss is:
write to a temporary file and close it
move the original to a backup location
move the temporary file to where the original was
if no errors, delete the backup
although when I say "common" what I really mean is that it should be
common, but probably isn't :-/ The sort of file handling that is
complicated and tedious to get right, and so most developers don't
bother, and those that do are re-inventing the wheel.
There's a couple of recipes in the Python Cookbook which might be
candidates. E.g. the first edition has recipes "Versioning Filenames"
by Robin Parmar and "Module: Versioned Backups" by Mitch Chapman.
What I DON'T mean is pathname utilities. Nor do I mean mini-applications
that operate on files, like renaming file extensions, deleting files
that meet some criterion, etc. I don't think they belong in the
standard library, and even if they do, they don't belong in this
My intention is to offer a standard set of tools so people can choose
the behaviour that suits their application best, rather than trying to
make file() a one-size-fits-all solution.
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