API Basics

Import and Installation
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!pip3 install hub
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import hub
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Default installation does not support GCS, audio, and video data. Installation of these features is described here.
Loading Hub Datasets
Hub datasets can be stored at a variety of storage locations using the appropriate dataset_path parameter below. We support S3, GCS, Activeloop storage, and are constantly adding to the list.
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# Load a Hub Dataset
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ds = hub.load('dataset_path', creds = {'optional'}, token = 'optional')
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# Load a Hub Dataset if it already exists (same as hub.load), or initialize 
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# a new Hub Dataset if it does not already exist (same as hub.empty)
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ds = hub.dataset('dataset_path', creds = {'optional'}, token = 'optional')
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Creating Hub Datasets
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# Create an empty hub dataset
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ds = hub.empty('dataset_path', creds = {'optional'}, token = 'optional')
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# Create an Hub Dataset with the same tensors as another dataset
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ds = hub.like(ds_object or 'dataset_path', creds = {'optional'}, token = 'optional')
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# Automatically create a Hub Dataset from another data source
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ds = hub.ingest('source_path', 'hub_dataset_path', creds = {'optional'}, token = 'optional')
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ds = hub.ingest_kaggle('kaggle_path', 'hub_dataset_path', creds = {'optional'}, token = 'optional')
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Deleting Datasets
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ds.delete()
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hub.delete('dataset_path', creds = {'optional'}, token = 'optional', token = 'optional')
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Creating Tensors
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# Specifying htype is recommended for maximizing performance.
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ds.create_tensor('my_tensor', htype = 'bbox')
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# Specifiying the correct compression is critical for images, videos, audio and 
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# other rich data types. 
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ds.create_tensor('songs', htype = 'audio', sample_compression = 'mp3')
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Creating Tensor Hierarchies
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ds.create_group('my_group')
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ds.my_group.create_tensor('my_tensor')
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ds.create_tensor('my_group/my_tensor') #Automatically creates the group 'my_group'
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Visualizing and Inspecting Datasets
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ds.visualize()
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ds.summary()
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Appending Data to Datasets
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ds.append('tensor_1': np.ones((1,4)), 'tensor_2': hub.read('image.jpg'))
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ds.my_group.append('tensor_1': np.ones((1,4)), 'tensor_2': hub.read('image.jpg'))
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Appending Data to Individual Tensors
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# Append a single sample
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ds.my_tensor.append(np.ones((1,4)))
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ds.my_tensor.append(hub.read('image.jpg'))
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# Append multiple samples. The first axis in the 
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# numpy array is assumed to be the sample axis for the tensor
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ds.my_tensor.extend(np.ones((5,1,4)))
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# Append multiple samples at the end of a tensor
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ds.my_tensor.extend([np.ones((1,4)), np.ones((3,4)), np.ones((2,4))])
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Appending Empty Samples or Skipping Samples
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# Data appended as None will be returned as an empty array
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ds.append('tensor_1': None, 'tensor_2': None)
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ds.my_tensor.append(None)
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# Empty arrays can be explicitly appended if the length of the shape 
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# of the empty array matches that of the other samples
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ds.boxes.append(np.zeros((0,4))
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Accessing Tensor Data
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# Read a tensor sample
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np_array = ds.my_tensor[0].numpy()
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text = ds.my_text_tensor[0].data() # Same as .numpy() if data can be returned as Numpy array
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bytes = ds.my_tensor[0].tobytes()
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# Read a tensor sample from a hierarchical group
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np_array_1 = ds.my_group.my_tensor_1[0].numpy()
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np_array_2 = ds.my_group.my_tensor_2[0].numpy()
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# Read multiple tensor samples into numpy array
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np_array = ds.my_tensor[0:10].numpy() 
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# Read multiple tensor samples into a list of numpy arrays
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np_array_list = ds.my_tensor[0:10].numpy(aslist=True)
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Maximizing performance
Make sure to use the with context when making any updates to datasets. 
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with ds:
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    ds.create_tensor('my_tensor')
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    for i in range(10):
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        ds.my_tensor.append(i)
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Adding User-Specified Metadata
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# Add or update dataset metadata
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ds.info.update(key1 = 'text', key2 = number)
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# Also can run ds.info.update({'key1'='value1', 'key2' = num_value})
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# Add or update tensor metadata
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ds.my_tensor.info.update(key1 = 'text', key2 = number)
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# Delete metadata
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ds.info.delete() #Delete all metadata
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ds.info.delete('key1') #Delete 1 key in metadata
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ds.info.delete(['key1', 'key2']) #Delete multiple keys in metadata
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Connecting Hub Datasets to ML Frameworks
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# PyTorch Dataloader
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dataloader = ds.pytorch(batch_size = 16, transform = {'images': torchvision_tform, 'labels': None}, num_workers = 2, scheduler = 'threaded')
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# TensorFlow Dataset
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ds_tensorflow = ds.tensorflow()
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Versioning Datasets
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# Commit data
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commit_id = ds.commit('Added 100 images of trucks')
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# Print the commit log
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log = ds.log()
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# Checkout a branch or commit 
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ds.checkout('branch_name' or commit_id)
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# Create a new branch
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ds.checkout('new_branch', create = True)
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# Examine differences between commits
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ds.diff()
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