Python: module for creating PID-based lockfile?

Question

I'm writing a Python script that may or may not (depending on a bunch of things) run for a long time, and I'd like to make sure that multiple instances (started via cron) don't step on each others toes. The logical way to do this seems to be a PID-based lockfile… But I don't want to re-invent the wheel if there is already code to do this.

So, is there a Python module out there which will manage the details of a PID-based lockfile?

Answer 1

This might be of help to you: lockfile

Answer 2

If you can use GPLv2, Mercurial has a module for that:

http://bitbucket.org/mirror/mercurial/src/tip/mercurial/lock.py

Example usage:

from mercurial import error, lock

try:
    l = lock.lock("/path/to/lock", timeout=600) # wait at most 10 minutes
    # do something
except error.LockHeld:
     # couldn't take the lock
else:
    l.release()

Answer 3

I believe you will find the necessary information here. The page in question refers to a package for building daemons in python: this process involves creating a PID lockfile.

Answer 4

There is a recipe on ActiveState on creating lockfiles.

To generate the filename you can use os.getpid() to get the PID.