LinkTransformer

LinkTransformer is a Python package for semantic record linkage, candidate retrieval, row transformation, clustering, and text classification over tabular data.

• Paper: https://arxiv.org/abs/2309.00789
• Website: https://linktransformer.github.io/
• Demo video: https://www.youtube.com/watch?v=Sn47nmCvV9M

Tutorials

• Link records with LinkTransformer: https://colab.research.google.com/drive/1OqUB8sqpUvrnC8oa_1RoOUzV6DaAKL4N?usp=sharing
• Train your own LinkTransformer model: https://colab.research.google.com/drive/1tHitPGjMMI2Nvh4wwA8rdcbYfbLaJDvg?usp=sharing
• Classify text with LinkTransformer: https://colab.research.google.com/drive/1hSh_p8j7LP2RfdtxrPslOfnogC_CbYw5?usp=sharing
• Demo app (Hugging Face Space): https://huggingface.co/spaces/96abhishekarora/linktransformer_merge
• Feature deck: https://www.dropbox.com/scl/fi/dquxru8bndlyf9na14cw6/A-python-package-to-do-easy-record-linkage-using-Transformer-models.pdf?rlkey=fiv7j6c0vgl901y940054eptk&dl=0

More tutorials are coming soon.

Installation

pip install linktransformer

Quick Start

import os
import pandas as pd
import linktransformer as lt

left_df = pd.DataFrame({"CompanyName": ["Tech Corporation"], "Country": ["USA"]})
right_df = pd.DataFrame({"CompanyName": ["Tech Corp"], "Country": ["USA"]})

out = lt.merge(
    left_df,
    right_df,
    on=["CompanyName", "Country"],
    model="sentence-transformers/all-MiniLM-L6-v2",
)
print(out[["CompanyName_x", "CompanyName_y", "score"]])

NEW RELEASE: End-to-end linkage Workflow: merge_k_judge (End-to-End Record Linkage)

merge_k_judge is the recommended end-to-end linkage API when you want both retrieval and LLM adjudication with confidence.

1. Retrieve top-k candidates with embeddings (merge_knn)
2. Judge each candidate pair with an LLM
3. Return match decisions and confidence scores

judged = lt.merge_k_judge(
    df1=left_df,
    df2=right_df,
    on=["CompanyName", "Country"],
    k=5,
    knn_sbert_model="sentence-transformers/all-MiniLM-L6-v2",
    judge_llm_model="gpt-4o-mini",
    llm_provider="openai",
    openai_key=os.getenv("OPENAI_API_KEY"),
)

# key output columns:
# - score (retrieval similarity)
# - is_match (bool)
# - confidence (float in [0, 1] when available)

You can also combine providers (for example OpenAI embeddings retrieval + Gemini judge) by setting knn_api_model, judge_llm_model, and llm_provider explicitly.

Core APIs

1) Link two dataframes

• lt.merge(...): semantic 1:1 / 1:m / m:1 linkage.
• lt.merge_knn(...): top-k candidate retrieval.
• lt.merge_blocking(...): run merge within blocks to do fuzzy merge within exact matches.
• lt.aggregate_rows(...): map fine rows to coarser labels.

matches = lt.merge_knn(
    left_df,
    right_df,
    on=["CompanyName", "Country"],
    model="sentence-transformers/all-MiniLM-L6-v2",
    k=3,
)

2) Transform rows with LLM prompts

Use lt.transform_rows(...) to normalize, rewrite, or standardize values in one or more columns. Eg : Fix OCR errors in the Column, Standardize names.

cleaned = lt.transform_rows(
    left_df,
    on=["CompanyName", "Country"],
    model="gpt-4o-mini",
    openai_key=os.getenv("OPENAI_API_KEY"),
    openai_prompt=(
        "Standardize organization names and country strings for record linkage. "
        "Return a JSON list in the same order."
    ),
)
# adds: transformed_CompanyName-Country

3) Cluster and deduplicate

• lt.cluster_rows(...): cluster semantically similar rows.
• lt.dedup_rows(...): cluster + keep representative rows.

deduped = lt.dedup_rows(
    left_df,
    on="CompanyName",
    model="sentence-transformers/all-MiniLM-L6-v2",
    cluster_type="agglomerative",
    cluster_params={"threshold": 0.7},
)

4) Evaluate matched pairs

• lt.evaluate_pairs(...): similarity over known pairs.
• lt.all_pair_combos_evaluate(...): dense pairwise scoring.

5) Classification

• lt.classify_rows(...): classify rows with HF or OpenAI chat models.
• lt.train_clf_model(...): train a custom row classifier.

6) Train linkage models

• lt.train_model(...): train a linkage model from paired or clustered data.

Provider Notes

• OpenAI key: set OPENAI_API_KEY or pass openai_key.
• Gemini key: set GEMINI_API_KEY or pass gemini_key.
• API embedding models and local SBERT models are both supported.
• For multi-column API retrieval, LinkTransformer serializes columns safely using <SEP>.

Test Naming Convention

Tests use test_lt_* naming to mirror the package API surface and make workflows discoverable.

Contributing

Issues and pull requests are welcome.

License

This project is licensed under the MIT License. See LICENSE.

Maintainers

• Sam Jones (samuelcaronnajones)
• Abhishek Arora (econabhishek)
• Yiyang Chen (oooyiyangc)