tf.keras.preprocessing.sequence.pad_sequences
Pads sequences to the same length.
tf.keras.preprocessing.sequence.pad_sequences(
sequences, maxlen=None, dtype='int32', padding='pre',
truncating='pre', value=0.0
)
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. |
© 2020 The TensorFlow Authors. All rights reserved.
Licensed under the Creative Commons Attribution License 3.0.
Code samples licensed under the Apache 2.0 License.
https://www.tensorflow.org/versions/r2.4/api_docs/python/tf/keras/preprocessing/sequence/pad_sequences