onpanda: The Companion Python Package for onPanda

Python package for onPanda: Efficient Annotation of On-Policy Alignment Data for LLMs and Agents via Token-Level Correction [project page]

Contents: Features | Install | Example Data | Quick Start | Main Modules | Iterative Correction API | Data Assumptions

▮ Features

• Parse .panda.json into SFT and preference-pair data (build_legacy_data_v1)
• Build token-level supervision data (build_token_level_supervision_data_v1/v2)
• Build Find-and-Replace correction training data (build_far_correction_data_v1)
• Verify and score Find-and-Replace outputs (FindAndReplaceVerifier)
• Benchmark Panda-CVL dataset
• Run iterative correction as a Proxy API (onpanda.server.iterative_correction_api)
• Build panda battle data from two arena result sets (build_panda_battle)

▮ Install

pip install onpanda -U

# Or want to run demos.
git clone https://github.com/on-panda/on-panda-python.git
pip install -e ./on-panda-python

# Example Data for demo
git clone https://github.com/on-panda/on-panda-example-data.git
ls on-panda-example-data/panda_json/

If you want to use tokenizers, install transformers separately.

▮ Quick Start

import onpanda

panda_path = (
    "../on-panda-example-data/panda_json/"
    "2025-08-19_how-many-1s_tokenizer-Qwen2.5.panda.json"
)
tokenizer=onpanda.utf8_tokenizer
# Use built-in utf8_tokenizer for a minimal runnable flow.
tree = onpanda.PandaTree(panda_path, tokenizer)

# 1) SFT + preference pairs
legacy = tree.build_legacy_data_v1()
print("sfts:", len(legacy["sfts"]))
print("preferences:", len(legacy["preferences"]))

# 2) Token-level supervision
token_level_v1 = tree.build_token_level_supervision_data_v1(
    tokenizer
)
print("token_level_v1:", len(token_level_v1))

# 3) Find-and-Replace correction data
adapter = onpanda.FindAndReplaceCorrectionAdapter(
    tokenizer
)
correction_data = tree.build_far_correction_data_v1(adapter)
print("correction_data:", len(correction_data))

Build from plain chat messages:

import onpanda

messages = [
    {"role": "user", "content": "5+7=?"},
    {"role": "assistant", "content": "12"},
]
panda_json = onpanda.messages_to_panda_tree(messages, uuid="demo")
# dump to xxx.panda.json

▮ Main Modules

• onpanda/parser.py: PandaTree and data conversion entrypoints
• onpanda/token_level_supervision_utils.py: token-level patch extraction and masks
• onpanda/correcting_model/far_correction_utils.py: FAR data builder and apply logic
• onpanda/correcting_model/verifier.py: FAR parser/locator/reward computation
• onpanda/correcting_model/panda_score_mixin.py: evaluation correction ability on Panda JSON
• onpanda/correcting_model/correcting_model.py: iterative correction workflow
• onpanda/server/iterative_correction_api.py: Flask wrapper for correction service
• onpanda/arena/panda_battle.py: build battle-style comparison data

▮ Iterative Correction API

Launch a proxy API server that return response using iterative_correction

python -m onpanda.server.iterative_correction_api --help

▮ Data Assumptions

• PandaTree is a parser for qualified, annotated Panda JSON.
• PandaTree preprocessing currently assumes:
  • Top-level field dialogs exists
  • Top-level field update_time exists
  • At least one dialog ends with an assistant message
  • If annotate.is_good is missing, latest dialog is treated as default good