[Python] How to have separate logging for instances of a class

I have a class that does some logging, and I want to be able to easily distinguish log messages that are from different instances of the class.

So, I thought I would create a logger object in the class __init__ method that has a unique identifier in the message formatter:

import logging

class Job:
def __init__(self, jobid):
self.logger = logging.getLogger(__name__)
self.logger.setLevel(logging.INFO)

handler = logging.StreamHandler()
formatter = logging.Formatter(
f'%(asctime)s %(levelname)-8s [{jobid}] %(message)s'
)

handler.setFormatter(formatter)
self.logger.addHandler(handler)

def logit(self, message):
self.logger.info(message)

j = Job(123)
k = Job(456)

j.logit('j starting')
k.logit('k starting')

j.logit('j ending')
k.logit('k ending')


When the code runs, I expect to see this output:

2025-07-15 14:46:01,192 INFO [123] j starting
2025-07-15 14:46:01,192 INFO [456] k starting
2025-07-15 14:46:01,192 INFO [123] j ending
2025-07-15 14:46:01,192 INFO [456] k ending


But instead, I see this:

2025-07-15 14:45:11,960 INFO [123] j starting
2025-07-15 14:45:11,960 INFO [456] j starting
2025-07-15 14:45:11,960 INFO [123] k starting
2025-07-15 14:45:11,960 INFO [456] k starting
2025-07-15 14:45:11,961 INFO [123] j ending
2025-07-15 14:45:11,961 INFO [456] j ending
2025-07-15 14:45:11,961 INFO [123] k ending
2025-07-15 14:45:11,961 INFO [456] k ending


All of the messages are logged twice, once with jobid 123 and again with jobid 456.

I suppose this happens because logging.getLogger(__name__) always produces the same logger object, which then gets multiple handlers added to it.

What is the solution here?

Do I need to pass a unique name to getLogger(), like f'{__name__}::{jobid}', to ensure that each logger object is unique?

Continue reading...