Create logger that prefixes log messages

Question

Let's say I have a client and server class:

import logging

class Client:
    def __init__(self, name):
        self.logger = logging.getLogger(self.__class__.__name__)
        self.name = name

    def foo(self):
        self.logger.warn('[%s] foo', self.name)

class Server:
    def __init__(self):
        self.logger = logging.getLogger(self.__class__.__name__)

    def bar(self):
        self.logger.warn('bar')

How could I make a logger for the client that will take care of the [self.name] prefix magically? The only Idea I have would be to set a global format including %(client)-prefix and using a custom filter for the Client. This seems unecessary complicated and global. I feel like there must be a simple way that I just don't see.

Answer 1

This can be done without any additional dependency using a custom LoggerAdapter:

import logging

class LoggerAdapter(logging.LoggerAdapter):
    def __init__(self, prefix, logger):
        super(LoggerAdapter, self).__init__(logger, {})
        self.prefix = prefix

    def process(self, msg, kwargs):
        return '[%s] %s' % (self.prefix, msg), kwargs

class Client:
    def __init__(self, name):
        logger = logging.getLogger(self.__class__.__name__) 
        self.logger = LoggerAdapter(name, logger)
        self.name = name

    def foo(self):
        self.logger.warning('foo: %s', 'bar')

client = Client('client1')
logging.basicConfig(format='%(message)s')
client.foo()

Which should print

[client1] foo: bar