Restrict multiple simultaneos executions of a Python program

Here you've a simple function to avoid a python script to be executed more than once at the same time:

def use_lock(func, lockfile):
    if not os.path.exists(lockfile):
        f = open(lockfile, 'w')
        f.write(str(os.getpid()))
        f.close()
        func()
        os.remove(lockfile)
        return True
    else:
        return None

To execute a function main() using a lock file "/var/run/myprogram.pid" just write:

use_lock(main, '/var/run/myprogram.pid')

Hope you find it useful.