Formatters

Thinlog provides three formatters covering structured output, plain text, and Telegram-ready HTML.

JsonFormatter

JsonFormatter serialises the entire LogRecord as a JSON string. Exception tracebacks are converted to structured dicts using structlog.tracebacks.ExceptionDictTransformer, giving you rich exception context (frames, locals) in machine-readable form.

See JsonFormatter in the API Reference.

TOML configuration:

[logging.formatters]
json = {"()" = "thinlog.formatters.json.JsonFormatter", show_locals = false}

Set show_locals = true to include local variables in exception tracebacks (helpful for debugging, but be mindful of sensitive data).

Stack info — when stack_info=True is passed to the log call and there is no exception, JsonFormatter parses the stack trace into structured frames via parse_stack_info().

MsgFormatter

MsgFormatter returns just the formatted message string, discarding all other record fields. Useful when you only need the human-readable message (e.g., for console output alongside a structured handler).

See MsgFormatter in the API Reference.

TOML configuration:

[logging.formatters]
msg = {"()" = "thinlog.formatters.msg.MsgFormatter"}

TelegramFormatter

TelegramFormatter wraps the log message in HTML <code> tags for the Telegram Bot API. It handles length limits automatically:

• Messages under 4096 characters → sent as a single <code> block.

• Longer messages → split into a truncated caption (up to 1024 chars) and the full raw text (sent as a document by TelegramHandler).

If the message is valid JSON, it is pretty-printed before formatting.

See TelegramFormatter in the API Reference.

TOML configuration:

[logging.formatters]
telegram = {"()" = "thinlog.formatters.telegram.TelegramFormatter"}