# tf.keras.layers.RNN

## Class RNN

Inherits From: Layer

Base class for recurrent layers.

#### Arguments:

• cell: A RNN cell instance. A RNN cell is a class that has: - a call(input_at_t, states_at_t) method, returning (output_at_t, states_at_t_plus_1). The call method of the cell can also take the optional argument constants, see section "Note on passing external constants" below. - a state_size attribute. This can be a single integer (single state) in which case it is the size of the recurrent state (which should be the same as the size of the cell output). This can also be a list/tuple of integers (one size per state). In this case, the first entry (state_size[0]) should be the same as the size of the cell output. It is also possible for cell to be a list of RNN cell instances, in which cases the cells get stacked on after the other in the RNN, implementing an efficient stacked RNN.
• return_sequences: Boolean. Whether to return the last output in the output sequence, or the full sequence.
• return_state: Boolean. Whether to return the last state in addition to the output.
• go_backwards: Boolean (default False). If True, process the input sequence backwards and return the reversed sequence.
• stateful: Boolean (default False). If True, the last state for each sample at index i in a batch will be used as initial state for the sample of index i in the following batch.
• unroll: Boolean (default False). If True, the network will be unrolled, else a symbolic loop will be used. Unrolling can speed-up a RNN, although it tends to be more memory-intensive. Unrolling is only suitable for short sequences.
• input_dim: dimensionality of the input (integer). This argument (or alternatively, the keyword argument input_shape) is required when using this layer as the first layer in a model.
• input_length: Length of input sequences, to be specified when it is constant. This argument is required if you are going to connect Flatten then Dense layers upstream (without it, the shape of the dense outputs cannot be computed). Note that if the recurrent layer is not the first layer in your model, you would need to specify the input length at the level of the first layer (e.g. via the input_shape argument)

Input shape: 3D tensor with shape (batch_size, timesteps, input_dim).

Output shape: - if return_state: a list of tensors. The first tensor is the output. The remaining tensors are the last states, each with shape (batch_size, units). - if return_sequences: 3D tensor with shape (batch_size, timesteps, units). - else, 2D tensor with shape (batch_size, units).

This layer supports masking for input data with a variable number
use an [Embedding](embeddings) layer with the mask_zero parameter
set to True.


# Note on using statefulness in RNNs

You can set RNN layers to be 'stateful', which means that the states
computed for the samples in one batch will be reused as initial states
for the samples in the next batch. This assumes a one-to-one mapping
between samples in different successive batches.

To enable statefulness:
- specify stateful=True in the layer constructor.
- specify a fixed batch size for your model, by passing
if sequential model:
batch_input_shape=(...) to the first layer in your model.
else for functional model with 1 or more Input layers:
batch_shape=(...) to all the first layers in your model.
This is the expected shape of your inputs
*including the batch size*.
It should be a tuple of integers, e.g. (32, 10, 100).
- specify shuffle=False when calling fit().

To reset the states of your model, call .reset_states() on either
a specific layer, or on your entire model.


# Note on specifying the initial state of RNNs

You can specify the initial state of RNN layers symbolically by
calling them with the keyword argument initial_state. The value of
initial_state should be a tensor or list of tensors representing
the initial state of the RNN layer.

You can specify the initial state of RNN layers numerically by
calling reset_states with the keyword argument states. The value of
states should be a numpy array or list of numpy arrays representing
the initial state of the RNN layer.


# Note on passing external constants to RNNs

You can pass "external" constants to the cell using the constants
keyword argument of RNN.__call__ (as well as RNN.call) method. This
requires that the cell.call method accepts the same keyword argument
constants. Such constants can be used to condition the cell
transformation on additional static inputs (not changing over time),
a.k.a. an attention mechanism.


Examples:

    # First, let's define a RNN Cell, as a layer subclass.

class MinimalRNNCell(keras.layers.Layer):

def __init__(self, units, **kwargs):
self.units = units
self.state_size = units
super(MinimalRNNCell, self).__init__(**kwargs)

def build(self, input_shape):
initializer='uniform',
name='kernel')
shape=(self.units, self.units),
initializer='uniform',
name='recurrent_kernel')
self.built = True

def call(self, inputs, states):
prev_output = states[0]
h = K.dot(inputs, self.kernel)
output = h + K.dot(prev_output, self.recurrent_kernel)
return output, [output]

# Let's use this cell in a RNN layer:

cell = MinimalRNNCell(32)
x = keras.Input((None, 5))
layer = RNN(cell)
y = layer(x)

# Here's how to use the cell to build a stacked RNN:

cells = [MinimalRNNCell(32), MinimalRNNCell(64)]
x = keras.Input((None, 5))
layer = RNN(cells)
y = layer(x)


## Properties

### activity_regularizer

Optional regularizer function for the output of this layer.

### inbound_nodes

Deprecated, do NOT use! Only for compatibility with external Keras.

### input

Retrieves the input tensor(s) of a layer.

Only applicable if the layer has exactly one input, i.e. if it is connected to one incoming layer.

#### Returns:

Input tensor or list of input tensors.

#### Raises:

• AttributeError: if the layer is connected to more than one incoming layers.

#### Raises:

• RuntimeError: If called in Eager mode.
• AttributeError: If no inbound nodes are found.

### input_mask

Retrieves the input mask tensor(s) of a layer.

Only applicable if the layer has exactly one inbound node, i.e. if it is connected to one incoming layer.

#### Raises:

• AttributeError: if the layer is connected to more than one incoming layers.

### input_shape

Retrieves the input shape(s) of a layer.

Only applicable if the layer has exactly one input, i.e. if it is connected to one incoming layer, or if all inputs have the same shape.

#### Returns:

Input shape, as an integer shape tuple (or list of shape tuples, one tuple per input tensor).

#### Raises:

• AttributeError: if the layer has no defined input_shape.
• RuntimeError: if called in Eager mode.

### outbound_nodes

Deprecated, do NOT use! Only for compatibility with external Keras.

### output

Retrieves the output tensor(s) of a layer.

Only applicable if the layer has exactly one output, i.e. if it is connected to one incoming layer.

#### Returns:

Output tensor or list of output tensors.

#### Raises:

• AttributeError: if the layer is connected to more than one incoming layers.
• RuntimeError: if called in Eager mode.

### output_mask

Retrieves the output mask tensor(s) of a layer.

Only applicable if the layer has exactly one inbound node, i.e. if it is connected to one incoming layer.

#### Raises:

• AttributeError: if the layer is connected to more than one incoming layers.

### output_shape

Retrieves the output shape(s) of a layer.

Only applicable if the layer has one output, or if all outputs have the same shape.

#### Returns:

Output shape, as an integer shape tuple (or list of shape tuples, one tuple per output tensor).

#### Raises:

• AttributeError: if the layer has no defined output shape.
• RuntimeError: if called in Eager mode.

### variables

Returns the list of all layer variables/weights.

#### Returns:

A list of variables.

### weights

Returns the list of all layer variables/weights.

#### Returns:

A list of variables.

## Methods

### __init__

__init__(
cell,
return_sequences=False,
return_state=False,
go_backwards=False,
stateful=False,
unroll=False,
**kwargs
)


### __call__

__call__(
inputs,
initial_state=None,
constants=None,
**kwargs
)


### __deepcopy__

__deepcopy__(memo)


### add_loss

add_loss(
losses,
inputs=None
)


Add loss tensor(s), potentially dependent on layer inputs.

Some losses (for instance, activity regularization losses) may be dependent on the inputs passed when calling a layer. Hence, when reusing the same layer on different inputs a and b, some entries in layer.losses may be dependent on a and some on b. This method automatically keeps track of dependencies.

The get_losses_for method allows to retrieve the losses relevant to a specific set of inputs.

Note that add_loss is not supported when executing eagerly. Instead, variable regularizers may be added through add_variable. Activity regularization is not supported directly (but such losses may be returned from Layer.call()).

#### Arguments:

• losses: Loss tensor, or list/tuple of tensors.
• inputs: If anything other than None is passed, it signals the losses are conditional on some of the layer's inputs, and thus they should only be run where these inputs are available. This is the case for activity regularization losses, for instance. If None is passed, the losses are assumed to be unconditional, and will apply across all dataflows of the layer (e.g. weight regularization losses).

#### Raises:

• RuntimeError: If called in Eager mode.

### add_update

add_update(
inputs=None
)


Add update op(s), potentially dependent on layer inputs.

Weight updates (for instance, the updates of the moving mean and variance in a BatchNormalization layer) may be dependent on the inputs passed when calling a layer. Hence, when reusing the same layer on different inputs a and b, some entries in layer.updates may be dependent on a and some on b. This method automatically keeps track of dependencies.

The get_updates_for method allows to retrieve the updates relevant to a specific set of inputs.

This call is ignored in Eager mode.

#### Arguments:

• updates: Update op, or list/tuple of update ops.
• inputs: If anything other than None is passed, it signals the updates are conditional on some of the layer's inputs, and thus they should only be run where these inputs are available. This is the case for BatchNormalization updates, for instance. If None, the updates will be taken into account unconditionally, and you are responsible for making sure that any dependency they might have is available at runtime. A step counter might fall into this category.

### add_variable

add_variable(
name,
shape,
dtype=None,
initializer=None,
regularizer=None,
trainable=True,
constraint=None,
partitioner=None
)


Adds a new variable to the layer, or gets an existing one; returns it.

#### Arguments:

• name: variable name.
• shape: variable shape.
• dtype: The type of the variable. Defaults to self.dtype or float32.
• initializer: initializer instance (callable).
• regularizer: regularizer instance (callable).
• trainable: whether the variable should be part of the layer's "trainable_variables" (e.g. variables, biases) or "non_trainable_variables" (e.g. BatchNorm mean, stddev). Note, if the current variable scope is marked as non-trainable then this parameter is ignored and any added variables are also marked as non-trainable.
• constraint: constraint instance (callable).
• partitioner: (optional) partitioner instance (callable). If provided, when the requested variable is created it will be split into multiple partitions according to partitioner. In this case, an instance of PartitionedVariable is returned. Available partitioners include tf.fixed_size_partitioner and tf.variable_axis_size_partitioner. For more details, see the documentation of tf.get_variable and the "Variable Partitioners and Sharding" section of the API guide.

#### Returns:

The created variable. Usually either a Variable or ResourceVariable instance. If partitioner is not None, a PartitionedVariable instance is returned.

#### Raises:

• RuntimeError: If called with partioned variable regularization and eager execution is enabled.

### add_weight

add_weight(
name,
shape,
dtype=None,
initializer=None,
regularizer=None,
trainable=True,
constraint=None
)


Adds a weight variable to the layer.

#### Arguments:

• name: String, the name for the weight variable.
• shape: The shape tuple of the weight.
• dtype: The dtype of the weight.
• initializer: An Initializer instance (callable).
• regularizer: An optional Regularizer instance.
• trainable: A boolean, whether the weight should be trained via backprop or not (assuming that the layer itself is also trainable).
• constraint: An optional Constraint instance.

#### Returns:

The created weight variable.

### apply

apply(
inputs,
*args,
**kwargs
)


Apply the layer on a input.

This simply wraps self.__call__.

#### Arguments:

• inputs: Input tensor(s).
• *args: additional positional arguments to be passed to self.call.
• **kwargs: additional keyword arguments to be passed to self.call.

#### Returns:

Output tensor(s).

### build

build(
instance,
input_shape
)


### call

call(
inputs,
training=None,
initial_state=None,
constants=None
)


### compute_mask

compute_mask(
inputs,
)


### compute_output_shape

compute_output_shape(
instance,
input_shape
)


### count_params

count_params()


Count the total number of scalars composing the weights.

#### Returns:

An integer count.

#### Raises:

• ValueError: if the layer isn't yet built (in which case its weights aren't yet defined).

### from_config

@classmethod
from_config(
cls,
config,
custom_objects=None
)


### get_config

get_config()


### get_initial_state

get_initial_state(inputs)


### get_input_at

get_input_at(node_index)


Retrieves the input tensor(s) of a layer at a given node.

#### Arguments:

• node_index: Integer, index of the node from which to retrieve the attribute. E.g. node_index=0 will correspond to the first time the layer was called.

#### Returns:

A tensor (or list of tensors if the layer has multiple inputs).

#### Raises:

• RuntimeError: If called in Eager mode.

### get_input_mask_at

get_input_mask_at(node_index)


Retrieves the input mask tensor(s) of a layer at a given node.

#### Arguments:

• node_index: Integer, index of the node from which to retrieve the attribute. E.g. node_index=0 will correspond to the first time the layer was called.

#### Returns:

A mask tensor (or list of tensors if the layer has multiple inputs).

### get_input_shape_at

get_input_shape_at(node_index)


Retrieves the input shape(s) of a layer at a given node.

#### Arguments:

• node_index: Integer, index of the node from which to retrieve the attribute. E.g. node_index=0 will correspond to the first time the layer was called.

#### Returns:

A shape tuple (or list of shape tuples if the layer has multiple inputs).

#### Raises:

• RuntimeError: If called in Eager mode.

### get_losses_for

get_losses_for(inputs)


Retrieves losses relevant to a specific set of inputs.

#### Arguments:

• inputs: Input tensor or list/tuple of input tensors.

#### Returns:

List of loss tensors of the layer that depend on inputs.

#### Raises:

• RuntimeError: If called in Eager mode.

### get_output_at

get_output_at(node_index)


Retrieves the output tensor(s) of a layer at a given node.

#### Arguments:

• node_index: Integer, index of the node from which to retrieve the attribute. E.g. node_index=0 will correspond to the first time the layer was called.

#### Returns:

A tensor (or list of tensors if the layer has multiple outputs).

#### Raises:

• RuntimeError: If called in Eager mode.

### get_output_mask_at

get_output_mask_at(node_index)


Retrieves the output mask tensor(s) of a layer at a given node.

#### Arguments:

• node_index: Integer, index of the node from which to retrieve the attribute. E.g. node_index=0 will correspond to the first time the layer was called.

#### Returns:

A mask tensor (or list of tensors if the layer has multiple outputs).

### get_output_shape_at

get_output_shape_at(node_index)


Retrieves the output shape(s) of a layer at a given node.

#### Arguments:

• node_index: Integer, index of the node from which to retrieve the attribute. E.g. node_index=0 will correspond to the first time the layer was called.

#### Returns:

A shape tuple (or list of shape tuples if the layer has multiple outputs).

#### Raises:

• RuntimeError: If called in Eager mode.

### get_updates_for

get_updates_for(inputs)


Retrieves updates relevant to a specific set of inputs.

#### Arguments:

• inputs: Input tensor or list/tuple of input tensors.

#### Returns:

List of update ops of the layer that depend on inputs.

#### Raises:

• RuntimeError: If called in Eager mode.

### get_weights

get_weights()


Returns the current weights of the layer.

#### Returns:

Weights values as a list of numpy arrays.

### reset_states

reset_states(states=None)


### set_weights

set_weights(weights)


Sets the weights of the layer, from Numpy arrays.

#### Arguments:

• weights: a list of Numpy arrays. The number of arrays and their shape must match number of the dimensions of the weights of the layer (i.e. it should match the output of get_weights).

#### Raises:

• ValueError: If the provided weights list does not match the layer's specifications.