Highlander is a decorator to help developers ensure that their python process is only running once. This is helpful when you have a python program running on a set schedule (i.e., a cron) and you do not want one run of the program to overlap with another run. Highlander accomplishes this by creating a file on disk that contains the current process identifier (PID) and creation time. If Highlander detects that a PID file currently exists it reads the PID and creation time from the file, checks to see if it exists. If it does exist, it ends the program and logs that the program was already running. If it does not exist, Highlander removes the old process information file, creates a new one, and executes the function associated with the decorator.

pip install highlander-one

from highlander import one

@one() # Create a PID file in the current working directory.
def long_running_operation():
    ...
    
    
from highlander import one

@one('/tmp/pid_file') # Create a PID file in a user-specified directory.
def long_running_operation():
    ...

• Add an argument to specify a timeout.
• Add an exclusive file lock to the process information file. I realize a race condition exists without this, but I want to release early and often.