TFRecord reader

Installation

pip3 install tfrecord

Usage

It's recommended to create an index file for each TFRecord file. Index file must be provided when using multiple workers, otherwise the loader may return duplicate records.

python3 -m tfrecord.tools.tfrecord2idx <tfrecord path> <index path>

Use TFRecordDataset to read TFRecord files in PyTorch.

import torch
from tfrecord.torch.dataset import TFRecordDataset

tfrecord_path = "/path/to/data.tfrecord"
index_path = None
description = {"image": "byte", "label": "float"}
dataset = TFRecordDataset(tfrecord_path, index_path, description)
loader = torch.utils.data.DataLoader(dataset, batch_size=32)

data = next(iter(loader))
print(data)

Use MultiTFRecordDataset to read multiple TFRecord files. This class samples from given tfrecord files with given probability.

import torch
from tfrecord.torch.dataset import MultiTFRecordDataset

tfrecord_pattern = "/path/to/{}.tfrecord"
index_pattern = "/path/to/{}.index"
splits = {
    "dataset1": 0.8,
    "dataset2": 0.2,
}
description = {"image": "byte", "label": "int"}
dataset = MultiTFRecordDataset(tfrecord_pattern, index_pattern, splits, description)
loader = torch.utils.data.DataLoader(dataset, batch_size=32)

data = next(iter(loader))
print(data)

Creating tfrecord files:

import tfrecord

writer = tfrecord.TFRecordWriter("/path/to/data.tfrecord")
writer.write({
    "image": (image_bytes, "byte"),
    "label": (label, "float"),
    "index": (index, "int")
})
writer.close()

Note: To write tfrecord files you also need an additional dependency:

pip3 install crc32c

Reading tfrecord files in python:

import tfrecord

loader = tfrecord.tfrecord_loader("/path/to/data.tfrecord", None, {
    "image": "byte",
    "label": "float",
    "index": "int"
})
for record in loader:
    print(record["label"])

Transforming input

You can optionally pass a function as transform argument to perform post processing of features before returning. This can for example be used to decode images or normalize colors to a certain range or pad variable length sequence.

import tfrecord
import cv2

def decode_image(features):
    # get BGR image from bytes
    features["image"] = cv2.imdecode(features["image"], -1)
    return features


description = {
    "image": "bytes",
}

dataset = tfrecord.torch.TFRecordDataset("/path/to/data.tfrecord",
                                         index_path=None,
                                         description=description,
                                         transform=decode_image)

data = next(iter(dataset))
print(data)