tf.keras.preprocessing.sequence

TensorFlow 1 version

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Pads sequences to the same length.

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Compat aliases for migration

See Migration guide for more details.

tf.compat.v1.keras.preprocessing.sequence.pad_sequences

tf.keras.preprocessing.sequence.pad_sequences(
    sequences, maxlen=None, dtype='int32', padding='pre',
    truncating='pre', value=0.0
)

Used in the notebooks

Used in the guide	Used in the tutorials
Masking and padding with Keras	Neural machine translation with attention Image captioning with visual attention TensorFlow Addons Networks : Sequence-to-Sequence NMT with Attention Mechanism Wiki Talk Comments Toxicity Prediction

This function transforms a list (of length num_samples) of sequences (lists of integers) into a 2D Numpy array of shape (num_samples, num_timesteps). num_timesteps is either the maxlen argument if provided, or the length of the longest sequence in the list.

Sequences that are shorter than num_timesteps are padded with value until they are num_timesteps long.

Sequences longer than num_timesteps are truncated so that they fit the desired length.

The position where padding or truncation happens is determined by the arguments padding and truncating, respectively. Pre-padding or removing values from the beginning of the sequence is the default.

sequence = [[1], [2, 3], [4, 5, 6]]
tf.keras.preprocessing.sequence.pad_sequences(sequence)
array([[0, 0, 1],
       [0, 2, 3],
       [4, 5, 6]], dtype=int32)

tf.keras.preprocessing.sequence.pad_sequences(sequence, value=-1)
array([[-1, -1,  1],
       [-1,  2,  3],
       [ 4,  5,  6]], dtype=int32)

tf.keras.preprocessing.sequence.pad_sequences(sequence, padding='post')
array([[1, 0, 0],
       [2, 3, 0],
       [4, 5, 6]], dtype=int32)

tf.keras.preprocessing.sequence.pad_sequences(sequence, maxlen=2)
array([[0, 1],
       [2, 3],
       [5, 6]], dtype=int32)

Arguments
`sequences`	List of sequences (each sequence is a list of integers).
`maxlen`	Optional Int, maximum length of all sequences. If not provided, sequences will be padded to the length of the longest individual sequence.
`dtype`	(Optional, defaults to int32). Type of the output sequences. To pad sequences with variable length strings, you can use `object`.
`padding`	String, 'pre' or 'post' (optional, defaults to 'pre'): pad either before or after each sequence.
`truncating`	String, 'pre' or 'post' (optional, defaults to 'pre'): remove values from sequences larger than `maxlen`, either at the beginning or at the end of the sequences.
`value`	Float or String, padding value. (Optional, defaults to 0.)

Returns
Numpy array with shape `(len(sequences), maxlen)`

Raises
`ValueError`	In case of invalid values for `truncating` or `padding`, or in case of invalid shape for a `sequences` entry.

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tf.keras / preprocessing / preprocessing.sequence.Overview

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Used in the notebooks

Arguments

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