> ## Documentation Index
> Fetch the complete documentation index at: https://docs.pixeltable.com/llms.txt
> Use this file to discover all available pages before exploring further.
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# Export data for ML training
This documentation page is also available as an interactive notebook. You can launch the notebook in
Kaggle or Colab, or download it for use with an IDE or local Jupyter installation, by clicking one of the
above links.
export const quartoRawHtml = [`
| Data type |
Use case |
| Images + labels |
Image classification |
| Text + embeddings |
Fine-tuning embeddings |
| Audio + transcripts |
Speech model training |
`, `
| Method |
Output |
Use case |
to_pytorch_dataset() |
PyTorch IterableDataset |
Direct training |
export_parquet() |
Parquet files |
External tools, sharing |
export_lancedb() |
LanceDB |
Vector search apps |
to_coco_dataset() |
COCO JSON |
Object detection |
`, `
| Format |
Shape |
Values |
Use |
'pt' |
CxHxW |
[0, 1] float32 |
PyTorch models |
'np' |
HxWxC |
[0, 255] uint8 |
NumPy processing |
`];
Convert Pixeltable data to PyTorch DataLoader format for model training.
## Problem
You have prepared training data—images with labels, text with
embeddings, or multimodal data—and need to export it for PyTorch model
training.
## Solution
**What’s in this recipe:**
* Convert query results to PyTorch Dataset
* Use with DataLoader for batch training
* Export to Parquet for external tools
You use `query.to_pytorch_dataset()` to create an iterable dataset
compatible with PyTorch DataLoader.
### Setup
```python theme={null}
%pip install -qU pixeltable torch torchvision
```
```python theme={null}
import pixeltable as pxt
import torch
from torch.utils.data import DataLoader
```
```python theme={null}
# Create a fresh directory
pxt.drop_dir('pytorch_demo', force=True)
pxt.create_dir('pytorch_demo')
```
Connected to Pixeltable database at: postgresql+psycopg://postgres:@/pixeltable?host=/Users/pjlb/.pixeltable/pgdata
Created directory 'pytorch\_demo'.
\
### Create sample training data
```python theme={null}
# Create table with images and labels
training_data = pxt.create_table(
'pytorch_demo/training_data', {'image': pxt.Image, 'label': pxt.Int}
)
```
Created table 'training\_data'.
```python theme={null}
# Insert sample images with labels
base_url = 'https://raw.githubusercontent.com/pixeltable/pixeltable/main/docs/resources/images'
samples = [
{'image': f'{base_url}/000000000036.jpg', 'label': 0}, # cat
{'image': f'{base_url}/000000000090.jpg', 'label': 1}, # other
{'image': f'{base_url}/000000000139.jpg', 'label': 1}, # other
]
training_data.insert(samples)
```
Inserting rows into \`training\_data\`: 3 rows \[00:00, 659.03 rows/s]
Inserted 3 rows with 0 errors.
3 rows inserted, 6 values computed.
### Export to PyTorch dataset
```python theme={null}
# Add a resize step to ensure all images have the same size
training_data.add_computed_column(
image_resized=training_data.image.resize((224, 224))
)
# Convert to PyTorch dataset
# 'pt' format returns images as CxHxW tensors with values in [0,1]
pytorch_dataset = training_data.select(
training_data.image_resized, training_data.label
).to_pytorch_dataset(image_format='pt')
```
Added 3 column values with 0 errors.
```python theme={null}
# Use with PyTorch DataLoader
dataloader = DataLoader(pytorch_dataset, batch_size=2)
# Get first batch to verify the shape
batch = next(iter(dataloader))
batch[
'image_resized'
].shape # Should be (2, 3, 224, 224) - batch_size x channels x height x width
```
torch.Size(\[2, 3, 224, 224])
### Export to Parquet for external tools
```python theme={null}
import tempfile
from pathlib import Path
# Export to Parquet for use with other ML tools
export_path = Path(tempfile.mkdtemp()) / 'training_data'
pxt.io.export_parquet(
training_data.select(training_data.label), # Non-image columns
parquet_path=export_path,
)
```
## Explanation
**Export methods:**
**Image format options:**
**DataLoader tips:**
* Data is cached to disk for efficient repeated loading
* Use `num_workers > 0` for parallel data loading
* Filter/transform data before export to reduce size
## See also
* [Sample data for
training](/howto/cookbooks/data/data-sampling) -
Stratified sampling
* [Import Parquet
files](/howto/cookbooks/data/data-import-parquet) -
Parquet import/export
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