ndarrow 0.1.1

PyArrow extension types for storing fixed-shape and ragged tensors

ndarrow

PyArrow extension types for efficiently storing tensors with variable or fixed shapes.

Overview

ndarrow provides two complementary PyArrow-native storage formats for tensor data:

• TensorArray — every element has exactly the same shape; the entire batch is backed by a single contiguous buffer.
• RaggedTensorArray — each element is a tensor whose leading dimension may vary, with a fixed inner_shape shared by all elements.

Both types store the element shape and NumPy dtype in the Arrow extension metadata, so they round-trip correctly through IPC and Parquet without any extra configuration.

Installation

pip install ndarrow

Usage

import numpy as np
import pyarrow as pa
import pyarrow.parquet as pq
from ndarrow import TensorArray, RaggedTensorArray

# Fixed-shape: one 64-dim embedding per sentence
sentence_embeddings = TensorArray.from_numpy(np.random.randn(3, 64))
# also accepts a list of arrays:
# sentence_embeddings = TensorArray.from_numpy([
#     np.random.randn(64)
#     for _ in range(3)
# ])

# Ragged: each sentence has a variable number of tokens, each with a 64-dim embedding
token_embeddings = RaggedTensorArray.from_numpy([
    np.random.randn(6, 64),
    np.random.randn(9, 64),
    np.random.randn(3, 64),
])

table = pa.table({"sentence_embeddings": sentence_embeddings, "token_embeddings": token_embeddings})
print(table.schema)
# sentence_embeddings: extension<ndarrow.tensor<TensorType>>
# token_embeddings:    extension<ndarrow.ragged_tensor<RaggedTensorType>>

# Round-trip through Parquet — type metadata is preserved
pq.write_table(table, "data.parquet")
table2 = pq.read_table("data.parquet")

embeddings_np = table2.column("sentence_embeddings").chunk(0).to_numpy()  # shape (3, 64)
tokens_list   = table2.column("token_embeddings").chunk(0).to_numpy()     # list of 3 arrays of shape (?, 64)