---
language:
  - en
  - zh
  - es
  - ur
license: apache-2.0
task_categories:
  - text-generation
tags:
  - code
  - multilingual
  - legesher
  - transpilation
  - tiny-aya-expedition
  - language-decoded
pretty_name: Language Decoded Data
size_categories:
  - 100K<n<1M
configs:
  - config_name: phase-2-the-stack-v1-condition-1-en-32k
    data_files:
      - split: train
        path: data/phase-2-the-stack-v1/condition-1-en-32k/train-*
      - split: validation
        path: data/phase-2-the-stack-v1/condition-1-en-32k/validation-*
  - config_name: phase-2-the-stack-v1-condition-1-en-5k
    data_files:
      - split: train
        path: data/phase-2-the-stack-v1/condition-1-en-5k/train-*
      - split: validation
        path: data/phase-2-the-stack-v1/condition-1-en-5k/validation-*
  - config_name: phase-2-the-stack-v1-condition-2-es-32k
    data_files:
      - split: train
        path: data/phase-2-the-stack-v1/condition-2-es-32k/train-*
      - split: validation
        path: data/phase-2-the-stack-v1/condition-2-es-32k/validation-*
  - config_name: phase-2-the-stack-v1-condition-2-es-5k
    data_files:
      - split: train
        path: data/phase-2-the-stack-v1/condition-2-es-5k/train-*
      - split: validation
        path: data/phase-2-the-stack-v1/condition-2-es-5k/validation-*
  - config_name: phase-2-the-stack-v1-condition-2-ur-32k
    data_files:
      - split: train
        path: data/phase-2-the-stack-v1/condition-2-ur-32k/train-*
      - split: validation
        path: data/phase-2-the-stack-v1/condition-2-ur-32k/validation-*
  - config_name: phase-2-the-stack-v1-condition-2-ur-5k
    data_files:
      - split: train
        path: data/phase-2-the-stack-v1/condition-2-ur-5k/train-*
      - split: validation
        path: data/phase-2-the-stack-v1/condition-2-ur-5k/validation-*
  - config_name: phase-2-the-stack-v1-condition-2-zh-32k
    data_files:
      - split: train
        path: data/phase-2-the-stack-v1/condition-2-zh-32k/train-*
      - split: validation
        path: data/phase-2-the-stack-v1/condition-2-zh-32k/validation-*
  - config_name: phase-2-the-stack-v1-condition-2-zh-5k
    data_files:
      - split: train
        path: data/phase-2-the-stack-v1/condition-2-zh-5k/train-*
      - split: validation
        path: data/phase-2-the-stack-v1/condition-2-zh-5k/validation-*
  - config_name: phase-2-the-stack-v1-condition-3-zh-5k
    data_files:
      - split: train
        path: data/phase-2-the-stack-v1/condition-3-zh-5k/train-*
      - split: validation
        path: data/phase-2-the-stack-v1/condition-3-zh-5k/validation-*
  - config_name: phase-2-the-stack-v1-condition-4-zh-5k
    data_files:
      - split: train
        path: data/phase-2-the-stack-v1/condition-4-zh-5k/train-*
      - split: validation
        path: data/phase-2-the-stack-v1/condition-4-zh-5k/validation-*
dataset_info:
  - config_name: phase-2-the-stack-v1-condition-1-en-32k
    features:
      - name: file_path
        dtype: string
      - name: code
        dtype: string
      - name: code_en
        dtype: string
      - name: language
        dtype: string
      - name: license
        dtype: string
      - name: token_count
        dtype: int32
    splits:
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        num_bytes: 403718262
        num_examples: 31818
      - name: validation
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        num_examples: 3536
    download_size: 164619518
    dataset_size: 446345172
  - config_name: phase-2-the-stack-v1-condition-1-en-5k
    features:
      - name: file_path
        dtype: string
      - name: code
        dtype: string
      - name: code_en
        dtype: string
      - name: language
        dtype: string
      - name: license
        dtype: string
      - name: token_count
        dtype: int32
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        num_examples: 4500
      - name: validation
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        num_examples: 500
    download_size: 22897728
    dataset_size: 61627514
  - config_name: phase-2-the-stack-v1-condition-2-es-32k
    features:
      - name: file_path
        dtype: string
      - name: code
        dtype: string
      - name: code_en
        dtype: string
      - name: language
        dtype: string
      - name: license
        dtype: string
      - name: token_count
        dtype: int32
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      - name: validation
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    download_size: 166000000
    dataset_size: 451132950
  - config_name: phase-2-the-stack-v1-condition-2-es-5k
    features:
      - name: file_path
        dtype: string
      - name: code
        dtype: string
      - name: code_en
        dtype: string
      - name: language
        dtype: string
      - name: license
        dtype: string
      - name: token_count
        dtype: int32
    splits:
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        num_bytes: 55864731
        num_examples: 4500
      - name: validation
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        num_examples: 500
    download_size: 23031674
    dataset_size: 62296826
  - config_name: phase-2-the-stack-v1-condition-2-ur-32k
    features:
      - name: file_path
        dtype: string
      - name: code
        dtype: string
      - name: code_en
        dtype: string
      - name: language
        dtype: string
      - name: license
        dtype: string
      - name: token_count
        dtype: int32
    splits:
      - name: train
        num_bytes: 415552907
        num_examples: 31818
      - name: validation
        num_bytes: 43879443
        num_examples: 3536
    download_size: 166000000
    dataset_size: 459432350
  - config_name: phase-2-the-stack-v1-condition-2-ur-5k
    features:
      - name: file_path
        dtype: string
      - name: code
        dtype: string
      - name: code_en
        dtype: string
      - name: language
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      - name: license
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      - name: token_count
        dtype: int32
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      - name: validation
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        num_examples: 500
    download_size: 23158039
    dataset_size: 63451977
  - config_name: phase-2-the-stack-v1-condition-2-zh-32k
    features:
      - name: file_path
        dtype: string
      - name: code
        dtype: string
      - name: code_en
        dtype: string
      - name: language
        dtype: string
      - name: license
        dtype: string
      - name: token_count
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    splits:
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        num_examples: 31818
      - name: validation
        num_bytes: 45065811
        num_examples: 3536
    download_size: 165387142
    dataset_size: 450581642
  - config_name: phase-2-the-stack-v1-condition-2-zh-5k
    features:
      - name: file_path
        dtype: string
      - name: code
        dtype: string
      - name: code_en
        dtype: string
      - name: language
        dtype: string
      - name: license
        dtype: string
      - name: token_count
        dtype: int32
    splits:
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        num_bytes: 55793642
        num_examples: 4500
      - name: validation
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        num_examples: 500
    download_size: 22978834
    dataset_size: 62216434
  - config_name: phase-2-the-stack-v1-condition-3-zh-5k
    features:
      - name: file_path
        dtype: large_string
      - name: code
        dtype: large_string
      - name: code_en
        dtype: string
      - name: language
        dtype: large_string
      - name: license
        dtype: large_string
      - name: token_count
        dtype: int64
      - name: source_type
        dtype: large_string
    splits:
      - name: train
        num_bytes: 40782466
        num_examples: 4500
      - name: validation
        num_bytes: 4531385
        num_examples: 500
    download_size: 17299185
    dataset_size: 45313851
  - config_name: phase-2-the-stack-v1-condition-4-zh-5k
    features:
      - name: filename
        dtype: string
      - name: content
        dtype: string
      - name: extension
        dtype: string
      - name: source
        dtype: string
      - name: quality_tier
        dtype: string
      - name: sha256
        dtype: string
      - name: byte_size
        dtype: int64
      - name: total_lines
        dtype: int64
      - name: cjk_ratio
        dtype: float64
      - name: has_cjk
        dtype: bool
    splits:
      - name: train
        num_bytes: 44246508
        num_examples: 6553
      - name: validation
        num_bytes: 7522476
        num_examples: 729
    download_size: 18300000
    dataset_size: 51768984
---

# Language Decoded | Multilingual Code Dataset

> **Note (2026-04-21):** Phase 2 configs have been renamed to `phase-2-the-stack-v1-*` and moved under `data/phase-2-the-stack-v1/`. Existing `load_dataset(...)` calls using the short `condition-*` names will no longer resolve. The short `condition-*` namespace is reserved for Phase 3 builds (streamed from The Stack v2, coming soon). See the _Loading the Dataset_ section below for updated config names.

Multilingual Python code datasets for the **Language Decoded** project (part of [Cohere's Tiny Aya Expedition](https://aya.for.ai)), investigating whether code's reasoning benefit for language models is **language-dependent** or **structure-dependent**.

## Research Question

> Does fine-tuning on non-English code (Python with translated keywords) improve multilingual reasoning as much as English code does?

Prior work ([Aryabumi et al., 2024 -- "To Code or Not to Code"](https://arxiv.org/abs/2408.10914)) demonstrated that including English code in pre-training data improves downstream reasoning performance by approximately 8%. However, that study only tested English code. This dataset enables the natural follow-up: does the reasoning benefit come from the _structure_ of code, or from the _language_ of its keywords?

## Dataset Description

This dataset provides filtered, quality-controlled Python source code in multiple configurations: the original English, three keyword-swapped variants (Chinese, Spanish, Urdu), a blended native+transpiled mix, and strictly native Chinese code. The source data is drawn from [bigcode/the-stack-dedup](https://huggingface.co/datasets/bigcode/the-stack-dedup) (Python subset), filtered for quality using the following criteria:

- AST-valid Python only (must parse without errors)
- Permissive licenses only (MIT, Apache-2.0, BSD, etc.)
- 10--1000 lines of code
- Minimum 21 GitHub stars
- No autogenerated files
- SHA-256 deduplication

Keyword-swapped variants are produced using [Legesher](https://github.com/legesher/legesher) v0.7.3, which translates Python reserved words (37 keywords, 72 builtins, 66 exceptions) into the target language while preserving code structure and semantics.

## Available Configs

Each condition is available in two sizes: `-32k` (full filtered corpus, ~31.8k train + ~3.5k validation) and `-5k` (stratified subset, 4.5k train + 500 validation). The `-5k` subsets are used for QLoRA fine-tuning on consumer GPUs.

| Config               | Condition   | Language | Description                                                  | Train  | Val   |
| -------------------- | ----------- | -------- | ------------------------------------------------------------ | ------ | ----- |
| `condition-1-en-32k` | 1 (control) | English  | Unmodified filtered Python from The Stack Dedup              | 31,818 | 3,536 |
| `condition-1-en-5k`  | 1 (control) | English  | Stratified 5k subset of condition-1                          | 4,500  | 500   |
| `condition-2-zh-32k` | 2           | Chinese  | Keyword-swapped Python via Legesher v0.7.3                   | 31,818 | 3,536 |
| `condition-2-zh-5k`  | 2           | Chinese  | Stratified 5k subset of condition-2-zh                       | 4,500  | 500   |
| `condition-2-es-32k` | 2           | Spanish  | Keyword-swapped Python via Legesher v0.7.3                   | 31,818 | 3,536 |
| `condition-2-es-5k`  | 2           | Spanish  | Stratified 5k subset of condition-2-es                       | 4,500  | 500   |
| `condition-2-ur-32k` | 2           | Urdu     | Keyword-swapped Python via Legesher v0.7.3                   | 31,818 | 3,536 |
| `condition-2-ur-5k`  | 2           | Urdu     | Stratified 5k subset of condition-2-ur                       | 4,500  | 500   |
| `condition-3-zh-5k`  | 3           | Chinese  | Blended: 3,486 native Chinese code + 1,514 transpiled Python | 4,500  | 500   |
| `condition-4-zh-5k`  | 4           | Chinese  | Strictly native Chinese code (no transpiled code)            | 6,553  | 729   |

## Schema

### Conditions 1--2

Used by: `condition-1-en-*`, `condition-2-zh-*`, `condition-2-es-*`, `condition-2-ur-*`

| Column        | Type   | Description                                                                                                                                          |
| ------------- | ------ | ---------------------------------------------------------------------------------------------------------------------------------------------------- |
| `code`        | string | Python source code. For condition-2 configs, this is the transpiled (keyword-swapped) version. For condition-1, this is the original English source. |
| `code_en`     | string | Original English Python source code. Identical to `code` for condition-1-en.                                                                         |
| `language`    | string | ISO 639-1 language code: `en`, `ur`, `zh`, or `es`.                                                                                                  |
| `file_path`   | string | Original file path in The Stack Dedup.                                                                                                               |
| `license`     | string | SPDX license identifier for the source file.                                                                                                         |
| `token_count` | int64  | Token count computed using the CohereLabs/tiny-aya-base tokenizer.                                                                                   |

### Condition 3

Used by: `condition-3-zh-5k`

Condition 3 blends native Chinese code with transpiled code and adds a `source_type` column to distinguish them. `code_en` is populated for transpiled rows (keeping them in sync with conditions 1--2) but null for native code rows, which have no English equivalent.

| Column        | Type        | Description                                                                        |
| ------------- | ----------- | ---------------------------------------------------------------------------------- |
| `file_path`   | string      | File identifier (native filename or transpiled file path)                          |
| `code`        | string      | The code content (native or transpiled)                                            |
| `code_en`     | string/null | English original -- populated for transpiled rows, null for native code rows       |
| `language`    | string      | ISO 639-1 language code (`zh`)                                                     |
| `license`     | string      | Source license (SPDX identifier, `UNKNOWN`, or `varies`)                           |
| `token_count` | int64       | Token count computed using the CohereLabs/tiny-aya-base tokenizer                  |
| `source_type` | string      | `"native"` (natively Chinese-authored) or `"transpiled"` (keyword-swapped English) |

### Condition 4

Used by: `condition-4-zh-5k`

Condition 4 contains strictly native Chinese code -- code written by developers who think and code in Chinese. This uses the same schema as the [language-decoded-community](https://huggingface.co/datasets/legesher/language-decoded-community) dataset rather than the transpilation schema, since there is no English original to reference.

| Column         | Type    | Description                                                    |
| -------------- | ------- | -------------------------------------------------------------- |
| `filename`     | string  | Original filename                                              |
| `content`      | string  | The code content                                               |
| `extension`    | string  | File extension (e.g., `.py`, `.c`, `.wenyan`)                  |
| `source`       | string  | Data source (e.g., `thestack`, `wenyan`, `program_in_chinese`) |
| `quality_tier` | string  | Quality rating: `A` (highest) through `D` (lowest)             |
| `sha256`       | string  | SHA-256 hash for deduplication                                 |
| `byte_size`    | int64   | File size in bytes                                             |
| `total_lines`  | int64   | Total line count                                               |
| `cjk_ratio`    | float64 | Ratio of CJK characters in the file                            |
| `has_cjk`      | bool    | Whether the file contains CJK characters                       |

## Experimental Conditions

The Language Decoded experiment uses a ladder of conditions to isolate the mechanism behind code's reasoning benefit:

| Condition   | Name                 | Purpose                                                                                   |
| ----------- | -------------------- | ----------------------------------------------------------------------------------------- |
| Baseline    | No fine-tuning       | Establishes the performance floor                                                         |
| Condition 1 | English code         | Tests whether code fine-tuning helps at all (replicates Aryabumi et al.)                  |
| Condition 2 | Keyword-swapped code | Tests whether the _language_ of keywords matters for the reasoning benefit                |
| Condition 3 | Mixed native sources | Tests whether diverse native-language code adds value beyond keyword swapping             |
| Condition 4 | Strictly native code | Tests whether code authored by native speakers carries unique signal beyond transpilation |

### The Experimental Ladder

- **Baseline --> 1**: Does code help at all?
- **1 --> 2**: Does the language of keywords matter?
- **2 --> 3**: Does diversity of native-language sources add value beyond keyword swap?
- **3 --> 4**: Does code written in the cultural context of a language carry something that transpiled+mixed can't?

## Usage

```python
from datasets import load_dataset

# Load full-size English code (control)
ds = load_dataset("legesher/language-decoded-data", "condition-1-en-32k")

# Load 5k subset (for QLoRA fine-tuning)
ds = load_dataset("legesher/language-decoded-data", "condition-1-en-5k")

# Load keyword-swapped variants
ds = load_dataset("legesher/language-decoded-data", "condition-2-zh-5k")
ds = load_dataset("legesher/language-decoded-data", "condition-2-es-5k")
ds = load_dataset("legesher/language-decoded-data", "condition-2-ur-5k")

# Load blended native + transpiled (condition 3)
ds = load_dataset("legesher/language-decoded-data", "condition-3-zh-5k")

# Load strictly native code (condition 4)
ds = load_dataset("legesher/language-decoded-data", "condition-4-zh-5k")

# Access splits
train = ds["train"]
val = ds["validation"]

# Filter condition-3 by source type
native_only = train.filter(lambda x: x["source_type"] == "native")
```

## Technical Details

| Parameter              | Value                                                                                                              |
| ---------------------- | ------------------------------------------------------------------------------------------------------------------ |
| Source dataset         | [bigcode/the-stack-dedup](https://huggingface.co/datasets/bigcode/the-stack-dedup) (Python subset)                 |
| Transpilation tool     | [Legesher](https://github.com/legesher/legesher) v0.7.3 (legesher-core, legesher-i18n)                             |
| Tokenizer              | CohereLabs/tiny-aya-base                                                                                           |
| Base model             | [CohereLabs/tiny-aya-base](https://huggingface.co/CohereLabs/tiny-aya-base) (3.35B params)                         |
| Train/validation split | 90% / 10% (seed 42)                                                                                                |
| File format            | Parquet (snappy compression)                                                                                       |
| Filtering criteria     | AST-valid, permissive licenses, 10--1000 lines, min 21 GitHub stars, no autogenerated files, SHA-256 deduplication |

## Limitations

- **Source bias**: The Stack Dedup skews toward popular, well-starred GitHub repositories, which may not represent the full diversity of Python code in the wild.
- **Keyword-only transpilation**: Legesher translates Python reserved words (keywords, builtins, exceptions) but leaves comments, docstrings, string literals, and variable/function names in their original language (typically English). This means condition-2 code is a hybrid of translated keywords and English identifiers.
- **Token count variation**: Transpiled code may have different token counts than the English original due to multi-byte characters (especially for Chinese and Urdu), even though the code structure is identical.
- **Single programming language**: Currently limited to Python. Results may not generalize to other programming languages.
- **Condition 4 scope**: Native Chinese code is limited to publicly available sources (The Stack, Wenyan, Program-in-Chinese, Qi, Mulan) and may not represent the full spectrum of Chinese-language programming.

## Citation

```bibtex
@misc{language-decoded-2026,
  title={Language Decoded: Investigating Language-Dependent vs. Structure-Dependent Reasoning Benefits of Code},
  author={Madison Edgar and Saad Ahmed Bazaz and Tom Sherborne and Rashik Shahjahan and Khojasteh Mirza and Sarah Jawaid and Rafay Mustafa and Sohaib Ahmed Bazaz},
  year={2026},
  publisher={Hugging Face},
  url={https://huggingface.co/datasets/legesher/language-decoded-data}
}
```

## Links

- [Legesher on GitHub](https://github.com/legesher/legesher)
- [Tiny Aya Expedition](https://aya.for.ai)
- [bigcode/the-stack-dedup](https://huggingface.co/datasets/bigcode/the-stack-dedup)
- [Language Decoded Community (native code)](https://huggingface.co/datasets/legesher/language-decoded-community)
- [Language Decoded Experiments (tracking)](https://huggingface.co/datasets/legesher/language-decoded-experiments)
- [Language Decoded LoRA (model hub)](https://huggingface.co/legesher/language-decoded-lora)

## License

Apache 2.0