safetensors-layer-grabber 0.1.0a2
Extracts all weights corresponding to a specific layer or block from large models saved in safetensors format, and exports them as a PyTorch-compatible state dict.
Requires Python: >=2

# safetensors-layer-grabber

Extracts all weights corresponding to a specific layer or block from large models saved
in [safetensors](https://github.com/huggingface/safetensors) format, and exports them as a PyTorch-compatible
state dict.

## Example

```bash
python -m safetensors_layer_grabber \
  --model-dir ~/models/my_model \
  --layer model.layers.12.mlp \
  --output layer12_mlp.ckpt
```

## Features

- **Targeted Extraction:** Extract weights corresponding to any layer or nested component by name prefix (e.g.
  `model.layers.8.self_attn`)
- **Flexible Output:** Choose your output filename, or default to `<layer>.ckpt`
- **Efficient:** Works directly with multipart safetensors files; no need to load the entire model

## Installation

```bash
pip install safetensors-layer-grabber
```

## Arguments

| Argument    | Required | Description                                                         |
|-------------|----------|---------------------------------------------------------------------|
| --model-dir | Yes      | Directory containing `.safetensors` files of the model              |
| --layer     | Yes      | Layer/component prefix to extract (e.g. `model.layers.8.self_attn`) |
| --output    | No       | Output file name (defaults to `<layer>.ckpt`)                       |

## Understanding Parameter Names

### In safetensors files

Safetensors model shards store parameters as key–tensor pairs, with keys like:

```
model.layers.8.self_attn.q_proj.weight
model.layers.8.self_attn.k_proj.weight
model.layers.8.self_attn.v_proj.bias
```

### In the extracted `.ckpt` file

When you use a prefix with `--layer`, **that prefix is stripped** from the keys in the saved state dict.

- **Example:**
    - Input safetensors key: `model.layers.8.self_attn.q_proj.weight`
    - Layer argument: `model.layers.8.self_attn`
    - Output key in `.ckpt`: `q_proj.weight`
- **Another example:**
    - Input safetensors key: `model.layers.10.mlp.fc1.weight`
    - Layer argument: `model.layers.10.mlp`
    - Output key in `.ckpt`: `fc1.weight`

#### Key Mapping Table

| Safetensors key                        | Layer argument           | Saved .ckpt key |
|----------------------------------------|--------------------------|-----------------|
| model.layers.8.self_attn.q_proj.weight | model.layers.8.self_attn | q_proj.weight   |
| model.layers.8.self_attn.k_proj.bias   | model.layers.8.self_attn | k_proj.bias     |
| model.layers.8.self_attn.inner.linear  | model.layers.8.self_attn | inner.linear    |

This makes the exported layer weights easy to load with `torch.load` or directly into submodules.

## FAQ & Notes

- If the specified `--layer` prefix **doesn't match any weights exactly**, the script will raise an exception and not
  write a file.
- If no `.safetensors` files are found in the directory, an error will be raised.

## Contributing

Contributions are welcome! Please submit pull requests or open issues on the GitHub repository.

## License

This project is licensed under the [MIT License](LICENSE).