Your riddle is likely is caused by the way multi-processing works in different operating systems. You don't mention, but your "run locally" is certainly Windows or MacOS, not a Linux or other Unix Flavor.
The thing is that multiprocessing on Linux (and up to a time ago on MacOS, but changed that on Python 3.8), used a system fork call when using multiprocessing: the current process is duplicatesd "as is" with all its defined variables and classes - since your sessionID is defined at import time, it stays the same in all subprocesess.
Windows lacks the fork call, and multiprocessing resorts to start a new Python interpreter which re-imports all modules from the current process (this leads to another, more common cause of confusion, where any code not guarded by an if __name__ == "__main__": on the entry Python file is re-executed). In your case the value for sessionID is regenerated.
Check the docs at: https://docs.python.org/3/library/multiprocessing.html#contexts-and-start-methods
So, if you want the variable to behave reliably and have teh same value across all processes when running multiprocessing, you should either pass it as a parameter to the target functions in the other processes, or use a proper structure meant to share values across processes as documented here:
https://docs.python.org/3/library/multiprocessing.html#sharing-state-between-processes
(you can also check this recent question about the same topic: why is a string printing 3 times instead of 1 when using time.sleep with multiprocessing imported?)
If you need a unique ID across files for each different process:
(As is more clear from the edit and comments)
Have a global (plain) dictionary which will work as a per-process registry for the IDs, and use a function to retrieve the ID - the function can use os.getpid() as a key to the registry.
file 1:
import os
import uuid
...
_id_registry = {}
def get_session_id():
return _id_registry.setdefault(os.getpid(), uuid.uuid4())
file2:
from file1 import get_session_id
sessionID = get_session_id()
(the setdefault dict method takes care of providing a new ID value if none was set)
NB.: the registry set up in this way will keep at most the master process ID (if multiprocessing is using fork mode) and itself - no data on the siblings, as each process will hold its own copy of the registry. If you need a working inter-process dictionary (which could hold a live registry for all processes, for example) you will probably be better using redis for it (https://redis.io - certainly one of the Python bindings have a transparent Python-mapping-over-redis, so you don´t have to worry with the semantics of it)
