⚡ fast-bunkai

⚡ FastBunkai is a Python library that splits long Japanese and English texts into natural sentences, providing a highly compatible API with megagonlabs/bunkai while its Rust core delivers roughly 40–285× faster segmentation than the original Python implementation. Existing bunkai users can swap to FastBunkai by importing it via from fast_bunkai import FastBunkai as Bunkai, making it a true drop-in replacement.

⚡ fast-bunkai は、日本語・英語の長い文章を自然な文単位に切り出すための Python ライブラリです。Pythonのみで書かれた megagonlabs/bunkai と高い互換性がある API を提供しつつ、内部を Rust で最適化することで、オリジナルの Python 版と比べ約40〜285倍の高速化を実現しています。既存の bunkai ユーザは from fast_bunkai import FastBunkai as Bunkai と書き換えるだけで簡単に移行できます。

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目次｜Table of Contents

• ✨ Highlights
• 🚀 Quick Start
• 🧰 CLI Examples
• 📊 Benchmarks
• 🧠 Architecture Snapshot
• 🛠️ Development Workflow
• 🧪 Testing & Quality Gates
• 🙏 Acknowledgements
• 📄 License
• 👤 Author

✨ Highlights

• 🔁 Drop-in replacement: mirrors the FastBunkai / Bunkai APIs and annotations, including Janome-based morphological spans.
• 🦀 Rust-powered core: heavy annotators (facemark, emoji, dot exceptions, indirect quotes, etc.) run inside a PyO3 module that releases the Python GIL.
• ⚡ Serious speed: real-world workloads observe 40×–285× faster segmentation than pure Python bunkai (details below).
• 🧵 Thread-safe by design: no global mutable state; calling FastBunkai concurrently from threads or asyncio tasks is supported.
• 🛫 CLI parity: ships a fast-bunkai executable compatible with bunkai’s pipe-friendly interface and --ma morphological mode.

🚀 Quick Start

Install

uv pip install fast-bunkai

Python Usage

from fast_bunkai import FastBunkai

splitter = FastBunkai()
text = "羽田から✈️出発して、友だちと🍣食べました。最高！また行きたいな😂でも、予算は大丈夫かな…?"
for sentence in splitter(text):
    print(sentence)

Output:

羽田から✈️出発して、友だちと🍣食べました。
最高！
また行きたいな😂
でも、予算は大丈夫かな…?

🧰 CLI Examples

fast-bunkai provides the same pipe-friendly command-line interface as bunkai.

echo -e '宿を予約しました♪!▁まだ2ヶ月も先だけど。▁早すぎかな(笑)楽しみです★\n2文書目です。▁改行を含みます。' \
  | uvx fast-bunkai

Output (sentence boundaries marked with │, newlines preserved via ▁):

宿を予約しました♪!▁│まだ2ヶ月も先だけど。▁│早すぎかな(笑)│楽しみです★
2文書目です。▁│改行を含みます。

Morphological output is also available:

echo -e '形態素解析し▁ます。結果を 表示します！' | uvx fast-bunkai --ma

形態素	名詞,一般,*,*,*,*,形態素,ケイタイソ,ケイタイソ
解析	名詞,サ変接続,*,*,*,*,解析,カイセキ,カイセキ
し	動詞,自立,*,*,サ変・スル,連用形,する,シ,シ
▁
EOS
ます	助動詞,*,*,*,特殊・マス,基本形,ます,マス,マス
。	記号,句点,*,*,*,*,。,。,。
EOS
結果	名詞,副詞可能,*,*,*,*,結果,ケッカ,ケッカ
を	助詞,格助詞,一般,*,*,*,を,ヲ,ヲ
	記号,空白,*,*,*,*, ,*,*
表示	名詞,サ変接続,*,*,*,*,表示,ヒョウジ,ヒョージ
し	動詞,自立,*,*,サ変・スル,連用形,する,シ,シ
ます	助動詞,*,*,*,特殊・マス,基本形,ます,マス,マス
！	記号,一般,*,*,*,*,！,！,！
EOS

📊 Benchmarks

Reproduce the bundled benchmark suite (correctness check + timing vs. bunkai):

uv run python scripts/benchmark.py --repeats 3 --jp-loops 100 --en-loops 100 --custom-loops 10

Latest local run (2025-10-11) reported:

Corpus	Docs	bunkai (mean)	fast-bunkai (mean)	Speedup
Japanese	200	253.92 ms	5.55 ms	45.72×
English	200	209.77 ms	4.94 ms	42.48×
Long text*	20	1330.95 ms	4.67 ms	285.10×

*Long text corpus contains mixed Japanese/English paragraphs with emojis and edge cases; the Rust pipeline processes characters in a single pass, whereas pure Python bunkai stacks regex scans, so the gap widens dramatically on longer documents.

Actual numbers vary by hardware, but the Rust core consistently outperforms pure Python bunkai by an order of magnitude or more.

🧠 Architecture Snapshot

• 🦀 Rust core (src/lib.rs): facemark & emoji annotators, dot/number exceptions, indirect quote handling, and more. Uses PyO3 abi3 bindings and releases the GIL with py.allow_threads.
• 😀 Emoji metadata (src/emoji_data.rs): generated via scripts/generate_emoji_data.py, mapping Unicode codepoints to bunkai-compatible categories.
• 🐍 Python layer (fast_bunkai/): wraps the Rust segment function, mirrors bunkai annotations with dataclasses, and builds Janome spans through MorphAnnotatorJanome for drop-in parity.

🛠️ Development Workflow

uv sync --reinstall
uv run python scripts/generate_emoji_data.py  # regenerate emoji table when emoji libs change
uv run tox -e pytests,lint,typecheck,rust-fmt,rust-clippy

For manual Rust checks:

cargo test face_mark_detection_matches_reference
cargo fmt --all
cargo clippy --all-targets -- -D warnings

🧪 Testing & Quality Gates

• ✅ pytest (tests/test_compatibility.py): ensures Japanese・English texts, emoji-heavy samples, and parallel execution match bunkai outputs.
• 🧹 Ruff: lint + format checks via tox -e lint,format-check.
• 🧠 Pyright: type-checks the Python API surface.
• 🧪 Rust unit tests: validate annotator logic remains in sync with reference behaviour.
• 📈 Benchmarks: scripts/benchmark.py validates speed + correctness; normally executed in CI to avoid long local runs.

🙏 Acknowledgements

FastBunkai stands on the shoulders of the megagonlabs/bunkai project—ありがとうございます！

📄 License

Apache License 2.0

👤 Author

Yuichi Tateno (@hotchpotch)