logging-bullet-train 0.4.0

A bullet-train style Python logging utils.

logging-bullet-train

A bullet-train style Python logging utility with colorful, emoji-enhanced log messages.

Documentation: https://allen2c.github.io/logging-bullet-train/

Features

• Colorful log levels and readable segment separators.
• ISO-8601 timestamps with zoneinfo timezone support.
• 45 built-in emoji themes plus custom theme mappings.
• Idempotent logger setup to avoid duplicate log lines.
• Configurable stream, color mode, propagation, and visible format sections.

Installation

pip install logging-bullet-train

For development:

poetry install --with dev

Usage

import logging

import logging_bullet_train as lbt

logger = lbt.set_logger("my_logger", level=logging.DEBUG)

logger.debug("debug message")
logger.info("info message")
logger.warning("warning message")
logger.error("error message")
logger.critical("critical message")
logger.log(1, "unknown message")

Sample output:

2026-04-27T08:08:12+00:00  🔎 DEBUG     my_logger:8  debug message
2026-04-27T08:08:12+00:00  💡 INFO      my_logger:9  info message
2026-04-27T08:08:12+00:00  ⭐ WARNING   my_logger:10  warning message

Configuration

import logging
import sys

from logging_bullet_train import set_logger

logger = set_logger(
    "app",
    level="INFO",
    theme="rocket",
    color="auto",
    stream=sys.stderr,
    timezone="Asia/Taipei",
    show_datetime=True,
    show_logger_name=True,
    show_lineno=True,
    propagate=False,
)

Logging defaults to stderr, which is the usual choice for logs because it keeps program output on stdout clean for shell pipelines.

Themes

Use a named theme:

logger = set_logger("app", theme="terminal")

Built-in themes:

from logging_bullet_train import level_emojis

print(sorted(level_emojis))

Use a custom theme mapping:

import logging

logger = set_logger("app", theme={logging.INFO: "ok"})

Custom themes are merged with the default theme, so you only need to override the levels you care about.

Color

set_logger("app", color=True)
set_logger("app", color=False)
set_logger("app", color="auto")
set_logger("app", color="always")
set_logger("app", color="never")

"auto" enables color only for TTY streams and respects the NO_COLOR environment variable.

Format Sections

set_logger(
    "app",
    show_datetime=False,
    show_logger_name=False,
    show_lineno=False,
)

Logger Attributes

set_logger("app", propagate=False, disabled=False)

set_logger() also avoids adding duplicate bullet-train handlers when called more than once for the same logger and stream. Pass replace_handlers=True to replace existing bullet-train handlers.

Manual Handler Setup

import logging

from logging_bullet_train import BulletTrainFormatter

handler = logging.StreamHandler()
handler.setFormatter(BulletTrainFormatter(theme="weather", color="auto"))

logger = logging.getLogger("manual")
logger.addHandler(handler)
logger.setLevel(logging.DEBUG)

Documentation

The documentation site is built with MkDocs Material.

Serve it locally:

poetry run mkdocs serve

Build it strictly:

poetry run mkdocs build --strict

GitHub Actions builds and deploys GitHub Pages when main is pushed.

License

MIT. See LICENSE.