[Python-Dev] Does Python need a file locking module (slightly higher level)?

Barry Warsaw barry at python.org
Mon Oct 22 15:37:03 CEST 2007


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On Oct 22, 2007, at 8:15 AM, skip at pobox.com wrote:

> I'm always daunted by the prospect of trying to implement file  
> locking.
> This just came up again in SpamBayes where we have never protected our
> pickle files from corruption when multiple processes access them
> simultaneously.  The presence of networked file systems and
> platform-independent locks make it a nasty little problem.  Maybe  
> I'm just
> showing my age.  Does fcntl.flock work over NFS and SMB and on  
> Windows?  If
> this is still as much of a mess as I remember, should Python provide a
> simple file locking module in the standard distribution?

If you want something like this, you might start by looking at  
Mailman's LockFile.py.  It has a particular set of semantics (such as  
lock breaking) that you might not be interested in, but it is, or can  
be, mostly de-Mailmanized for use as a general library module.  In  
the particular use case it is designed for, it's been quite stable  
for many years.  Essentially it provides an NFS-safe lock file  
implementation.

- -Barry

http://codebrowse.launchpad.net/~mailman-coders/mailman/3.0/annotate/ 
barry%40python.org-20071011032203-w1j8qrmtlpkrvay4? 
file_id=mailmanlockfile.py-20070507165525-0o0kligrooe34vyc-172

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