TFRecord reader and writer
This library allows reading and writing tfrecord files efficiently in python. The library also provides an IterableDataset reader of tfrecord files for PyTorch. Currently uncompressed and compressed gzip TFRecords are supported.
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. You can create an index file for an individual tfrecord file with this utility program:
python3 -m tfrecord.tools.tfrecord2idx <tfrecord path> <index path>
To create ".tfidnex" files for all ".tfrecord" files in a directory run:
tfrecord2idx <data dir>
Reading & Writing tf.train.Example
Reading tf.Example records in PyTorch
Use TFRecordDataset to read TFRecord files in PyTorch.
import torch
from tfrecord.torch.dataset import TFRecordDataset
tfrecord_path = "/tmp/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 = "/tmp/{}.tfrecord"
index_pattern = "/tmp/{}.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)Infinite and finite PyTorch dataset
By default, MultiTFRecordDataset is infinite, meaning that it samples the data forever. You can make it finite by providing the appropriate flag
dataset = MultiTFRecordDataset(..., infinite=False)
Shuffling the data
Both TFRecordDataset and MultiTFRecordDataset automatically shuffle the data when you provide a queue size.
dataset = TFRecordDataset(..., shuffle_queue_size=1024)
Transforming input data
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("/tmp/data.tfrecord",
index_path=None,
description=description,
transform=decode_image)
data = next(iter(dataset))
print(data)Writing tf.Example records in Python
import tfrecord
writer = tfrecord.TFRecordWriter("/tmp/data.tfrecord")
writer.write({
"image": (image_bytes, "byte"),
"label": (label, "float"),
"index": (index, "int")
})
writer.close()Reading tf.Example records in Python
import tfrecord
loader = tfrecord.tfrecord_loader("/tmp/data.tfrecord", None, {
"image": "byte",
"label": "float",
"index": "int"
})
for record in loader:
print(record["label"])Reading & Writing tf.train.SequenceExample
SequenceExamples can be read and written using the same methods shown above with an extra argument
(sequence_description for reading and sequence_datum for writing) which cause the respective
read/write functions to treat the data as a SequenceExample.
Writing SequenceExamples to file
import tfrecord
writer = tfrecord.TFRecordWriter("/tmp/data.tfrecord")
writer.write({'length': (3, 'int'), 'label': (1, 'int')},
{'tokens': ([[0, 0, 1], [0, 1, 0], [1, 0, 0]], 'int'), 'seq_labels': ([0, 1, 1], 'int')})
writer.write({'length': (3, 'int'), 'label': (1, 'int')},
{'tokens': ([[0, 0, 1], [1, 0, 0]], 'int'), 'seq_labels': ([0, 1], 'int')})
writer.close()Reading SequenceExamples in python
Reading from a SequenceExample yeilds a tuple containing two elements.
import tfrecord
context_description = {"length": "int", "label": "int"}
sequence_description = {"tokens": "int", "seq_labels": "int"}
loader = tfrecord.tfrecord_loader("/tmp/data.tfrecord", None,
context_description,
sequence_description=sequence_description)
for context, sequence_feats in loader:
print(context["label"])
print(sequence_feats["seq_labels"])Read SequenceExamples in PyTorch
As described in the section on Transforming Input, one can pass a function as the transform argument to
perform post processing of features. This should be used especially for the sequence features as these are
variable length sequence and need to be padded out before being batched.
import torch
import numpy as np
from tfrecord.torch.dataset import TFRecordDataset
PAD_WIDTH = 5
def pad_sequence_feats(data):
context, features = data
for k, v in features.items():
features[k] = np.pad(v, ((0, PAD_WIDTH - len(v)), (0, 0)), 'constant')
return (context, features)
context_description = {"length": "int", "label": "int"}
sequence_description = {"tokens": "int ", "seq_labels": "int"}
dataset = TFRecordDataset("/tmp/data.tfrecord",
index_path=None,
description=context_description,
transform=pad_sequence_feats,
sequence_description=sequence_description)
loader = torch.utils.data.DataLoader(dataset, batch_size=32)
data = next(iter(loader))
print(data)Alternatively, you could choose to implement a custom collate_fn in order to assemble the batch,
for example, to perform dynamic padding.
import torch
import numpy as np
from tfrecord.torch.dataset import TFRecordDataset
def collate_fn(batch):
from torch.utils.data._utils import collate
from torch.nn.utils import rnn
context, feats = zip(*batch)
feats_ = {k: [torch.Tensor(d[k]) for d in feats] for k in feats[0]}
return (collate.default_collate(context),
{k: rnn.pad_sequence(f, True) for (k, f) in feats_.items()})
context_description = {"length": "int", "label": "int"}
sequence_description = {"tokens": "int ", "seq_labels": "int"}
dataset = TFRecordDataset("/tmp/data.tfrecord",
index_path=None,
description=context_description,
transform=pad_sequence_feats,
sequence_description=sequence_description)
loader = torch.utils.data.DataLoader(dataset, batch_size=32, collate_fn=collate_fn)
data = next(iter(loader))
print(data)