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logging-eager-conversion (RUF065)

Preview (since 0.13.2) · Related issues · View source

This rule is unstable and in preview. The --preview flag is required for use.

What it does

Checks for eager string conversion of arguments to logging calls.

Why is this bad?

Arguments to logging calls will be formatted as strings automatically, so it is unnecessary and less efficient to eagerly format the arguments before passing them in.

Known problems

This rule detects uses of the logging module via a heuristic. Specifically, it matches against:

  • Uses of the logging module itself (e.g., import logging; logging.info(...)).
  • Uses of flask.current_app.logger (e.g., from flask import current_app; current_app.logger.info(...)).
  • Objects whose name starts with log or ends with logger or logging, when used in the same file in which they are defined (e.g., logger = logging.getLogger(); logger.info(...)).
  • Imported objects marked as loggers via the lint.logger-objects setting, which can be used to enforce these rules against shared logger objects (e.g., from module import logger; logger.info(...), when lint.logger-objects is set to ["module.logger"]).

Example

import logging

logging.basicConfig(format="%(message)s", level=logging.INFO)

user = "Maria"

logging.info("%s - Something happened", str(user))

Use instead:

import logging

logging.basicConfig(format="%(message)s", level=logging.INFO)

user = "Maria"

logging.info("%s - Something happened", user)

Options

References