set log level with structlog

I am trying to setup structlog and set log level. My code looks like this:

import structlog
import logging

filepath=open("out.log",'a')

logging.basicConfig(
  level=logging.INFO
)

structlog.configure(
    processors=[structlog.stdlib.filter_by_level],
    wrapper_class=structlog.BoundLogger,
    context_class=dict,
    logger_factory=structlog.PrintLoggerFactory(filepath),
)
logger = structlog.getLogger()
logger.info('test')

This fails:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.8/site-packages/structlog/_base.py", line 189, in _proxy_to_logger
    args, kw = self._process_event(method_name, event, event_kw)
  File "/usr/local/lib/python3.8/site-packages/structlog/_base.py", line 149, in _process_event
    event_dict = proc(self._logger, method_name, event_dict)
  File "/usr/local/lib/python3.8/site-packages/structlog/stdlib.py", line 381, in filter_by_level
    if logger.isEnabledFor(_NAME_TO_LEVEL[name]):
AttributeError: 'PrintLogger' object has no attribute 'isEnabledFor'

Okay, sure. I am not supposed to use PrintLogger with stdlib processors. But I want to filter by log level (because that’s how logging usually works, eh?) So how do I do that? I assume I need to use some other logger factory, but which one? Of course structlog.stdlib.LoggerFactory works, but it doesn’t redirect to a file.

So I said: okay I will create my own filter:

def my_filter_by_level(logger, name, event_dict):
    if True:
        return event_dict
    else:
        raise DropEvent

processors=[my_filter_by_level],

And when I try to use the logger I get:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.8/site-packages/structlog/_base.py", line 190, in _proxy_to_logger
    return getattr(self._logger, method_name)(*args, **kw)
TypeError: msg() got an unexpected keyword argument 'organization'

This is coming from

logger = logger.bind(**{"organization": "blah"})

but… why? What is wrong with my processor?

Answer

Well, the reason my filter didn’t work is this: https://www.structlog.org/en/stable/processors.html#adapting

Last filter in chain is special and can’t just return a dictionary.

And the following filter did the trick:

def my_filter_by_level(logger, name, event_dict):
    this_level = structlog.stdlib._NAME_TO_LEVEL[name]
    set_level = structlog.stdlib._NAME_TO_LEVEL[loglevel]
    if this_level >= set_level:
        return event_dict
    else:
        raise structlog.DropEvent

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