Context Manager

PidFile can be used as a context manager:

from pid import PidFile

with PidFile():
  do_something()

Decorator

PidFile can also be used a a decorator:

from pid.decorator import pidfile

@pidfile()
def main():
  pass

if __name__ == "__main__":
  main()

Exception Order

In default mode PidFile will try to acquire a file lock before anything else. This means that normally you get a PidFileAlreadyLockedError instead of the PidFileAlreadyRunningError when running a program twice.

If you just want to know if a program is already running its easiest to catch just PidFileError since it will capture all possible PidFile exceptions.

Behaviour

Changes in version 2.0.0 and going forward:

• pid is now friendly with daemon context managers such as python-daemon where the PidFile context manager is passed as a parameter. The new corrected behaviour will ensure the process environment is determinde at the time of acquiring/checking the lock. Prior behaviour would determine the process environment when instancing the class which may result in incorrect determination of the PID in the case of a process forking after instancing PidFile.

• Cleanup of pidfile on termination is done using atexit module. The default SIGTERM handler doesn't cleanly exit and therefore the atexit registered functions will not execute. A custom handler which triggers the atexit registered functions for cleanup will override the default SIGTERM handler. If a prior signal handler has been configured, then it will not be overridden.