logformat 0.1.0

logfmt logging for Python

logformat - logfmt logging for Python

• implements the same value escaping as the logfmt library used by Grafana Loki
• implements a logging.Formatter so it works with any library using the standard library logging
• implements a convenience wrapper around logging.Logging for specifying structured fields via kwargs

import logging

import logformat

logfmt_handler = logging.StreamHandler()
logfmt_handler.setFormatter(logformat.LogfmtFormatter())
logging.basicConfig(handlers=[logfmt_handler], level=logging.INFO)

logger = logformat.get_logger()

logger.warning("this seems off", some_id=33)

Will output a line like:

time=2025-03-23T06:21:36Z level=warning msg="this seems off" some_id=33

exc_info and stack_info are supported via backtrace=True and stack=True (which will add same-named fields).

In the main method of a script you should always catch any exception and log them as errors, so that unexpected errors show up properly in your log file. This library makes this easy by providing a log_uncaught decorator:

logger = logformat.get_logger()

@logger.log_uncaught
def run():
    # your script
    ...

This library intentionally doesn't provide any pretty terminal output but the produced logs can be viewed with the logfmt CLI (since that tool again uses the logfmt library that this library is compatible with).

Alternatives

• structlog's get_logger returns Any. While there's a typed alternative that's a bit of a footgun.

• logfmter doesn't include the time by default, names the time field when by default and the level field at by default, doesn't use ISO dates by default and isn't compatible with the Go logfmt library as of March 2025