tf.keras.utils.pad_sequences  |  TensorFlow v2.16.1 (original) (raw)

Pads sequences to the same length.

View aliases

Main aliases

tf.keras.preprocessing.sequence.pad_sequences

tf.keras.utils.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
Understanding masking & padding 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_timestepsare 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]] keras.utils.pad_sequences(sequence) array([[0, 0, 1], [0, 2, 3], [4, 5, 6]], dtype=int32)

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

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

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

Args
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 thanmaxlen, 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)