tf.keras.Sequential

Class Sequential

Inherits From: Model

Aliases:

• Class tf.keras.Sequential
• Class tf.keras.models.Sequential

Defined in tensorflow/python/keras/_impl/keras/engine/sequential.py.

Linear stack of layers.

Arguments:

• layers: list of layers to add to the model.

Example:

# Optionally, the first layer can receive an `input_shape` argument:
model = Sequential()
model.add(Dense(32, input_shape=(500,)))
# Afterwards, we do automatic shape inference:
model.add(Dense(32))

# This is identical to the following:
model = Sequential()
model.add(Dense(32, input_dim=500))

# And to the following:
model = Sequential()
model.add(Dense(32, batch_input_shape=(None, 500)))

# Note that you can also omit the `input_shape` argument:
# In that case the model gets built the first time you call `fit` (or other
# training and evaluation methods).
model = Sequential()
model.add(Dense(32))
model.add(Dense(32))
model.compile(optimizer=optimizer, loss=loss)
# This builds the model for the first time:
model.fit(x, y, batch_size=32, epochs=10)

# Note that when using this delayed-build pattern (no input shape specified),
# the model doesn't have any weights until the first call
# to a training/evaluation method (since it isn't yet built):
model = Sequential()
model.add(Dense(32))
model.add(Dense(32))
model.weights  # returns []

# Whereas if you specify the input shape, the model gets built continuously
# as you are adding layers:
model = Sequential()
model.add(Dense(32, input_shape=(500,)))
model.add(Dense(32))
model.weights  # returns list of length 4

When using the delayed-build pattern (no input shape specified), you can
choose to manually build your model by calling `build(batch_input_shape)`:
model = Sequential()
model.add(Dense(32))
model.add(Dense(32))
model.build((None, 500))
model.weights  # returns list of length 4

Properties

activity_regularizer

Optional regularizer function for the output of this layer.

dtype

graph

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.

Returns:

Input mask tensor (potentially None) or list of input mask tensors.

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.

input_spec

Gets the network's input specs.

Returns:

A list of InputSpec instances (one per input to the model) or a single instance if the model has only one input.

layers

losses

Retrieves the network's losses.

Will only include losses that are either unconditional, or conditional on inputs to this model (e.g. will not include losses that depend on tensors that aren't inputs to this model).

Returns:

A list of loss tensors.

name

non_trainable_variables

non_trainable_weights

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.

Returns:

Output mask tensor (potentially None) or list of output mask tensors.

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.

scope_name

state_updates

Returns the updates from all layers that are stateful.

This is useful for separating training updates and state updates, e.g. when we need to update a layer's internal state during prediction.

Returns:

A list of update ops.

stateful

trainable_variables

trainable_weights

updates

Retrieves the network's updates.

Will only include updates that are either unconditional, or conditional on inputs to this model (e.g. will not include updates that were created by layers of this model outside of the model).

Effectively, network.updates behaves like layer.updates.

Concrete example:

bn = keras.layers.BatchNormalization()
x1 = keras.layers.Input(shape=(10,))
_ = bn(x1)  # This creates 2 updates.

x2 = keras.layers.Input(shape=(10,))
y2 = bn(x2)  # This creates 2 more updates.

# The BN layer has now 4 updates.
self.assertEqual(len(bn.updates), 4)

# Let's create a model from x2 to y2.
model = keras.models.Model(x2, y2)

# The model does not list all updates from its underlying layers,
# but only the updates that are relevant to it. Updates created by layers
# outside of the model are discarded.
self.assertEqual(len(model.updates), 2)

# If you keep calling the model, you append to its updates, just like
# what happens for a layer.
x3 = keras.layers.Input(shape=(10,))
y3 = model(x3)
self.assertEqual(len(model.updates), 4)

# But if you call the inner BN layer independently, you don't affect
# the model's updates.
x4 = keras.layers.Input(shape=(10,))
_ = bn(x4)
self.assertEqual(len(model.updates), 4)

Returns:

A list of update ops.

uses_learning_phase

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__(
    layers=None,
    name=None
)

Initialize self. See help(type(self)) for accurate signature.

__call__

__call__(
    inputs,
    *args,
    **kwargs
)

Wrapper around self.call(), for handling internal references.

If a Keras tensor is passed: - We call self._add_inbound_node(). - If necessary, we build the layer to match the shape of the input(s). - We update the _keras_history of the output tensor(s) with the current layer. This is done as part of _add_inbound_node().

Arguments:

• inputs: Can be a tensor or list/tuple of tensors.
• *args: Additional positional arguments to be passed to call(). Only allowed in subclassed Models with custom call() signatures. In other cases, Layer inputs must be passed using the inputs argument and non-inputs must be keyword arguments.
• **kwargs: Additional keyword arguments to be passed to call().

Returns:

Output of the layer's call method.

Raises:

• ValueError: in case the layer is missing shape information for its build call.
• TypeError: If positional arguments are passed and this Layer is not a subclassed Model.

__deepcopy__

__deepcopy__(memo)

__setattr__

__setattr__(
    name,
    value
)

Implement setattr(self, name, value).

add

add(layer)

Adds a layer instance on top of the layer stack.

Arguments:

• layer: layer instance.

Raises:

• TypeError: If layer is not a layer instance.
• ValueError: In case the layer argument does not know its input shape.
• ValueError: In case the layer argument has multiple output tensors, or is already connected somewhere else (forbidden in Sequential models).

add_loss

add_loss(
    *args,
    **kwargs
)

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(
    updates,
    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
)

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(input_shape=None)

Creates the variables of the layer.

call

call(
    inputs,
    training=None,
    mask=None
)

Calls the model on new inputs.

In this case call just reapplies all ops in the graph to the new inputs (e.g. build a new computational graph from the provided inputs).

Arguments:

• inputs: A tensor or list of tensors.
• training: Boolean or boolean scalar tensor, indicating whether to run the Network in training mode or inference mode.
• mask: A mask or list of masks. A mask can be either a tensor or None (no mask).

Returns:

A tensor if there is a single output, or a list of tensors if there are more than one outputs.

compile

compile(
    optimizer,
    loss=None,
    metrics=None,
    loss_weights=None,
    sample_weight_mode=None,
    weighted_metrics=None,
    target_tensors=None,
    **kwargs
)

Configures the model for training.

Arguments:

• optimizer: String (name of optimizer) or optimizer instance. See optimizers.
• loss: String (name of objective function) or objective function. See losses. If the model has multiple outputs, you can use a different loss on each output by passing a dictionary or a list of losses. The loss value that will be minimized by the model will then be the sum of all individual losses.
• metrics: List of metrics to be evaluated by the model during training and testing. Typically you will use metrics=['accuracy']. To specify different metrics for different outputs of a multi-output model, you could also pass a dictionary, such as metrics={'output_a': 'accuracy'}.
• loss_weights: Optional list or dictionary specifying scalar coefficients (Python floats) to weight the loss contributions of different model outputs. The loss value that will be minimized by the model will then be the weighted sum of all individual losses, weighted by the loss_weights coefficients. If a list, it is expected to have a 1:1 mapping to the model's outputs. If a tensor, it is expected to map output names (strings) to scalar coefficients.
• sample_weight_mode: If you need to do timestep-wise sample weighting (2D weights), set this to "temporal". None defaults to sample-wise weights (1D). If the model has multiple outputs, you can use a different sample_weight_mode on each output by passing a dictionary or a list of modes.
• weighted_metrics: List of metrics to be evaluated and weighted by sample_weight or class_weight during training and testing.
• target_tensors: By default, Keras will create placeholders for the model's target, which will be fed with the target data during training. If instead you would like to use your own target tensors (in turn, Keras will not expect external Numpy data for these targets at training time), you can specify them via the target_tensors argument. It can be a single tensor (for a single-output model), a list of tensors, or a dict mapping output names to target tensors.
• **kwargs: These arguments are passed to tf.Session.run.

Raises:

• ValueError: In case of invalid arguments for optimizer, loss, metrics or sample_weight_mode.

compute_mask

compute_mask(
    inputs,
    mask
)

Computes an output mask tensor.

Arguments:

• inputs: Tensor or list of tensors.
• mask: Tensor or list of tensors.

Returns:

None or a tensor (or list of tensors, one per output tensor of the layer).

compute_output_shape

compute_output_shape(input_shape)

Computes the output shape of the layer.

Assumes that the layer will be built to match that input shape provided.

Arguments:

• input_shape: Shape tuple (tuple of integers) or list of shape tuples (one per output tensor of the layer). Shape tuples can include None for free dimensions, instead of an integer.

Returns:

An input shape tuple.

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).

evaluate

evaluate(
    x=None,
    y=None,
    batch_size=None,
    verbose=1,
    sample_weight=None,
    steps=None
)

Returns the loss value & metrics values for the model in test mode.

Computation is done in batches.

Arguments:

• x: Numpy array of test data (if the model has a single input), or list of Numpy arrays (if the model has multiple inputs). If input layers in the model are named, you can also pass a dictionary mapping input names to Numpy arrays. x can be None (default) if feeding from TensorFlow data tensors.
• y: Numpy array of target (label) data (if the model has a single output), or list of Numpy arrays (if the model has multiple outputs). If output layers in the model are named, you can also pass a dictionary mapping output names to Numpy arrays. y can be None (default) if feeding from TensorFlow data tensors.
• batch_size: Integer or None. Number of samples per evaluation step. If unspecified, batch_size will default to 32.
• verbose: 0 or 1. Verbosity mode. 0 = silent, 1 = progress bar.
• sample_weight: Optional Numpy array of weights for the test samples, used for weighting the loss function. You can either pass a flat (1D) Numpy array with the same length as the input samples (1:1 mapping between weights and samples), or in the case of temporal data, you can pass a 2D array with shape (samples, sequence_length), to apply a different weight to every timestep of every sample. In this case you should make sure to specify sample_weight_mode="temporal" in compile().
• steps: Integer or None. Total number of steps (batches of samples) before declaring the evaluation round finished. Ignored with the default value of None.

Returns:

Scalar test loss (if the model has a single output and no metrics) or list of scalars (if the model has multiple outputs and/or metrics). The attribute model.metrics_names will give you the display labels for the scalar outputs.

Raises:

• ValueError: in case of invalid arguments.

evaluate_generator

evaluate_generator(
    generator,
    steps=None,
    max_queue_size=10,
    workers=1,
    use_multiprocessing=False
)

Evaluates the model on a data generator.

The generator should return the same kind of data as accepted by test_on_batch.

Arguments:

• generator: Generator yielding tuples (inputs, targets) or (inputs, targets, sample_weights) or an instance of Sequence (keras.utils.Sequence) object in order to avoid duplicate data when using multiprocessing.
• steps: Total number of steps (batches of samples) to yield from generator before stopping. Optional for Sequence: if unspecified, will use the len(generator) as a number of steps.
• max_queue_size: maximum size for the generator queue
• workers: Integer. Maximum number of processes to spin up when using process-based threading. If unspecified, workers will default to 1. If 0, will execute the generator on the main thread.
• use_multiprocessing: Boolean. If True, use process-based threading. If unspecified, use_multiprocessing will default to False. Note that because this implementation relies on multiprocessing, you should not pass non-picklable arguments to the generator as they can't be passed easily to children processes.

Returns:

Scalar test loss (if the model has a single output and no metrics) or list of scalars (if the model has multiple outputs and/or metrics). The attribute model.metrics_names will give you the display labels for the scalar outputs.

Raises:

• ValueError: in case of invalid arguments.

Raises:

• ValueError: In case the generator yields data in an invalid format.

fit

fit(
    x=None,
    y=None,
    batch_size=None,
    epochs=1,
    verbose=1,
    callbacks=None,
    validation_split=0.0,
    validation_data=None,
    shuffle=True,
    class_weight=None,
    sample_weight=None,
    initial_epoch=0,
    steps_per_epoch=None,
    validation_steps=None,
    **kwargs
)

Trains the model for a fixed number of epochs (iterations on a dataset).

Arguments:

• x: Numpy array of training data (if the model has a single input), or list of Numpy arrays (if the model has multiple inputs). If input layers in the model are named, you can also pass a dictionary mapping input names to Numpy arrays. x can be None (default) if feeding from TensorFlow data tensors.
• y: Numpy array of target (label) data (if the model has a single output), or list of Numpy arrays (if the model has multiple outputs). If output layers in the model are named, you can also pass a dictionary mapping output names to Numpy arrays. y can be None (default) if feeding from TensorFlow data tensors.
• batch_size: Integer or None. Number of samples per gradient update. If unspecified, batch_size will default to 32.
• epochs: Integer. Number of epochs to train the model. An epoch is an iteration over the entire x and y data provided. Note that in conjunction with initial_epoch, epochs is to be understood as "final epoch". The model is not trained for a number of iterations given by epochs, but merely until the epoch of index epochs is reached.
• verbose: Integer. 0, 1, or 2. Verbosity mode. 0 = silent, 1 = progress bar, 2 = one line per epoch.
• callbacks: List of keras.callbacks.Callback instances. List of callbacks to apply during training. See callbacks.
• validation_split: Float between 0 and 1. Fraction of the training data to be used as validation data. The model will set apart this fraction of the training data, will not train on it, and will evaluate the loss and any model metrics on this data at the end of each epoch. The validation data is selected from the last samples in the x and y data provided, before shuffling.
• validation_data: tuple (x_val, y_val) or tuple (x_val, y_val, val_sample_weights) on which to evaluate the loss and any model metrics at the end of each epoch. The model will not be trained on this data. validation_data will override validation_split.
• shuffle: Boolean (whether to shuffle the training data before each epoch) or str (for 'batch'). 'batch' is a special option for dealing with the limitations of HDF5 data; it shuffles in batch-sized chunks. Has no effect when steps_per_epoch is not None.
• class_weight: Optional dictionary mapping class indices (integers) to a weight (float) value, used for weighting the loss function (during training only). This can be useful to tell the model to "pay more attention" to samples from an under-represented class.
• sample_weight: Optional Numpy array of weights for the training samples, used for weighting the loss function (during training only). You can either pass a flat (1D) Numpy array with the same length as the input samples (1:1 mapping between weights and samples), or in the case of temporal data, you can pass a 2D array with shape (samples, sequence_length), to apply a different weight to every timestep of every sample. In this case you should make sure to specify sample_weight_mode="temporal" in compile().
• initial_epoch: Integer. Epoch at which to start training (useful for resuming a previous training run).
• steps_per_epoch: Integer or None. Total number of steps (batches of samples) before declaring one epoch finished and starting the next epoch. When training with input tensors such as TensorFlow data tensors, the default None is equal to the number of samples in your dataset divided by the batch size, or 1 if that cannot be determined.
• validation_steps: Only relevant if steps_per_epoch is specified. Total number of steps (batches of samples) to validate before stopping.
• **kwargs: Used for backwards compatibility.

Returns:

A History object. Its History.history attribute is a record of training loss values and metrics values at successive epochs, as well as validation loss values and validation metrics values (if applicable).

Raises:

• RuntimeError: If the model was never compiled.
• ValueError: In case of mismatch between the provided input data and what the model expects.

fit_generator

fit_generator(
    generator,
    steps_per_epoch=None,
    epochs=1,
    verbose=1,
    callbacks=None,
    validation_data=None,
    validation_steps=None,
    class_weight=None,
    max_queue_size=10,
    workers=1,
    use_multiprocessing=False,
    shuffle=True,
    initial_epoch=0
)

Fits the model on data yielded batch-by-batch by a Python generator.

The generator is run in parallel to the model, for efficiency. For instance, this allows you to do real-time data augmentation on images on CPU in parallel to training your model on GPU.

The use of keras.utils.Sequence guarantees the ordering and guarantees the single use of every input per epoch when using use_multiprocessing=True.

Arguments:

• generator: A generator or an instance of Sequence (keras.utils.Sequence) object in order to avoid duplicate data when using multiprocessing. The output of the generator must be either - a tuple (inputs, targets) - a tuple (inputs, targets, sample_weights). This tuple (a single output of the generator) makes a single batch. Therefore, all arrays in this tuple must have the same length (equal to the size of this batch). Different batches may have different sizes. For example, the last batch of the epoch is commonly smaller than the others, if the size of the dataset is not divisible by the batch size. The generator is expected to loop over its data indefinitely. An epoch finishes when steps_per_epoch batches have been seen by the model.
• steps_per_epoch: Total number of steps (batches of samples) to yield from generator before declaring one epoch finished and starting the next epoch. It should typically be equal to the number of samples of your dataset divided by the batch size. Optional for Sequence: if unspecified, will use the len(generator) as a number of steps.
• epochs: Integer, total number of iterations on the data.
• verbose: Verbosity mode, 0, 1, or 2.
• callbacks: List of callbacks to be called during training.
• validation_data: This can be either - a generator for the validation data - a tuple (inputs, targets) - a tuple (inputs, targets, sample_weights).
• validation_steps: Only relevant if validation_data is a generator. Total number of steps (batches of samples) to yield from generator before stopping. Optional for Sequence: if unspecified, will use the len(validation_data) as a number of steps.
• class_weight: Dictionary mapping class indices to a weight for the class.
• max_queue_size: Integer. Maximum size for the generator queue. If unspecified, max_queue_size will default to 10.
• workers: Integer. Maximum number of processes to spin up when using process-based threading. If unspecified, workers will default to 1. If 0, will execute the generator on the main thread.
• use_multiprocessing: Boolean. If True, use process-based threading. If unspecified, use_multiprocessing will default to False. Note that because this implementation relies on multiprocessing, you should not pass non-picklable arguments to the generator as they can't be passed easily to children processes.
• shuffle: Boolean. Whether to shuffle the order of the batches at the beginning of each epoch. Only used with instances of Sequence (keras.utils.Sequence). Has no effect when steps_per_epoch is not None.
• initial_epoch: Epoch at which to start training (useful for resuming a previous training run)

Returns:

A `History` object.

Example:

def generate_arrays_from_file(path):
    while 1:
        f = open(path)
        for line in f:
            # create numpy arrays of input data
            # and labels, from each line in the file
            x1, x2, y = process_line(line)
            yield ({'input_1': x1, 'input_2': x2}, {'output': y})
        f.close()

model.fit_generator(generate_arrays_from_file('/my_file.txt'),
                    steps_per_epoch=10000, epochs=10)

Raises:

• ValueError: In case the generator yields data in an invalid format.

from_config

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

Instantiates a Model from its config (output of get_config()).

Arguments:

• config: Model config dictionary.
• custom_objects: Optional dictionary mapping names (strings) to custom classes or functions to be considered during deserialization.

Returns:

A model instance.

Raises:

• ValueError: In case of improperly formatted config dict.

get_config

get_config()

Returns the config of the layer.

A layer config is a Python dictionary (serializable) containing the configuration of a layer. The same layer can be reinstantiated later (without its trained weights) from this configuration.

The config of a layer does not include connectivity information, nor the layer class name. These are handled by Network (one layer of abstraction above).

Returns:

Python dictionary.

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_layer

get_layer(
    name=None,
    index=None
)

Retrieves a layer based on either its name (unique) or index.

If name and index are both provided, index will take precedence. Indices are based on order of horizontal graph traversal (bottom-up).

Arguments:

• name: String, name of layer.
• index: Integer, index of layer.

Returns:

A layer instance.

Raises:

• ValueError: In case of invalid layer name or index.

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()

Retrieves the weights of the model.

Returns:

A flat list of Numpy arrays.

load_weights

load_weights(
    filepath,
    by_name=False
)

Loads all layer weights from a HDF5 save file.

If by_name is False (default) weights are loaded based on the network's topology, meaning the architecture should be the same as when the weights were saved. Note that layers that don't have weights are not taken into account in the topological ordering, so adding or removing layers is fine as long as they don't have weights.

If by_name is True, weights are loaded into layers only if they share the same name. This is useful for fine-tuning or transfer-learning models where some of the layers have changed.

Arguments:

• filepath: String, path to the weights file to load.
• by_name: Boolean, whether to load weights by name or by topological order.

Raises:

• ImportError: If h5py is not available.

pop

pop()

Removes the last layer in the model.

Raises:

• TypeError: if there are no layers in the model.

predict

predict(
    x,
    batch_size=None,
    verbose=0,
    steps=None
)

Generates output predictions for the input samples.

Computation is done in batches.

Arguments:

• x: The input data, as a Numpy array (or list of Numpy arrays if the model has multiple outputs).
• batch_size: Integer. If unspecified, it will default to 32.
• verbose: Verbosity mode, 0 or 1.
• steps: Total number of steps (batches of samples) before declaring the prediction round finished. Ignored with the default value of None.

Returns:

Numpy array(s) of predictions.

Raises:

• ValueError: In case of mismatch between the provided input data and the model's expectations, or in case a stateful model receives a number of samples that is not a multiple of the batch size.

predict_classes

predict_classes(
    x,
    batch_size=32,
    verbose=0
)

Generate class predictions for the input samples.

The input samples are processed batch by batch.

Arguments:

• x: input data, as a Numpy array or list of Numpy arrays (if the model has multiple inputs).
• batch_size: integer.
• verbose: verbosity mode, 0 or 1.

Returns:

A numpy array of class predictions.

predict_generator

predict_generator(
    generator,
    steps=None,
    max_queue_size=10,
    workers=1,
    use_multiprocessing=False,
    verbose=0
)

Generates predictions for the input samples from a data generator.

The generator should return the same kind of data as accepted by predict_on_batch.

Arguments:

• generator: Generator yielding batches of input samples or an instance of Sequence (keras.utils.Sequence) object in order to avoid duplicate data when using multiprocessing.
• steps: Total number of steps (batches of samples) to yield from generator before stopping. Optional for Sequence: if unspecified, will use the len(generator) as a number of steps.
• max_queue_size: Maximum size for the generator queue.
• workers: Integer. Maximum number of processes to spin up when using process-based threading. If unspecified, workers will default to 1. If 0, will execute the generator on the main thread.
• use_multiprocessing: Boolean. If True, use process-based threading. If unspecified, use_multiprocessing will default to False. Note that because this implementation relies on multiprocessing, you should not pass non-picklable arguments to the generator as they can't be passed easily to children processes.
• verbose: verbosity mode, 0 or 1.

Returns:

Numpy array(s) of predictions.

Raises:

• ValueError: In case the generator yields data in an invalid format.

predict_on_batch

predict_on_batch(x)

Returns predictions for a single batch of samples.

Arguments:

• x: Input samples, as a Numpy array.

Returns:

Numpy array(s) of predictions.

predict_proba

predict_proba(
    x,
    batch_size=32,
    verbose=0
)

Generates class probability predictions for the input samples.

The input samples are processed batch by batch.

Arguments:

• x: input data, as a Numpy array or list of Numpy arrays (if the model has multiple inputs).
• batch_size: integer.
• verbose: verbosity mode, 0 or 1.

Returns:

A Numpy array of probability predictions.

reset_states

reset_states()

save

save(
    filepath,
    overwrite=True,
    include_optimizer=True
)

Saves the model to a single HDF5 file.

The savefile includes: - The model architecture, allowing to re-instantiate the model. - The model weights. - The state of the optimizer, allowing to resume training exactly where you left off.

This allows you to save the entirety of the state of a model in a single file.

Saved models can be reinstantiated via keras.models.load_model. The model returned by load_model is a compiled model ready to be used (unless the saved model was never compiled in the first place).

Arguments:

• filepath: String, path to the file to save the weights to.
• overwrite: Whether to silently overwrite any existing file at the target location, or provide the user with a manual prompt.
• include_optimizer: If True, save optimizer's state together.

Example:

from keras.models import load_model

model.save('my_model.h5')  # creates a HDF5 file 'my_model.h5'
del model  # deletes the existing model

# returns a compiled model
# identical to the previous one
model = load_model('my_model.h5')

save_weights

save_weights(
    filepath,
    overwrite=True
)

Dumps all layer weights to a HDF5 file.

The weight file has: - layer_names (attribute), a list of strings (ordered names of model layers). - For every layer, a group named layer.name - For every such layer group, a group attribute weight_names, a list of strings (ordered names of weights tensor of the layer). - For every weight in the layer, a dataset storing the weight value, named after the weight tensor.

Arguments:

• filepath: String, path to the file to save the weights to.
• overwrite: Whether to silently overwrite any existing file at the target location, or provide the user with a manual prompt.

Raises:

• ImportError: If h5py is not available.

set_weights

set_weights(weights)

Sets the weights of the model.

Arguments:

• weights: A list of Numpy arrays with shapes and types matching the output of model.get_weights().

summary

summary(
    line_length=None,
    positions=None,
    print_fn=None
)

Prints a string summary of the network.

Arguments:

• line_length: Total length of printed lines (e.g. set this to adapt the display to different terminal window sizes).
• positions: Relative or absolute positions of log elements in each line. If not provided, defaults to [.33, .55, .67, 1.].
• print_fn: Print function to use. Defaults to print. It will be called on each line of the summary. You can set it to a custom function in order to capture the string summary.

test_on_batch

test_on_batch(
    x,
    y,
    sample_weight=None
)

Test the model on a single batch of samples.

Arguments:

• x: Numpy array of test data, or list of Numpy arrays if the model has multiple inputs. If all inputs in the model are named, you can also pass a dictionary mapping input names to Numpy arrays.
• y: Numpy array of target data, or list of Numpy arrays if the model has multiple outputs. If all outputs in the model are named, you can also pass a dictionary mapping output names to Numpy arrays.
• sample_weight: Optional array of the same length as x, containing weights to apply to the model's loss for each sample. In the case of temporal data, you can pass a 2D array with shape (samples, sequence_length), to apply a different weight to every timestep of every sample. In this case you should make sure to specify sample_weight_mode="temporal" in compile().

Returns:

Scalar test loss (if the model has a single output and no metrics) or list of scalars (if the model has multiple outputs and/or metrics). The attribute model.metrics_names will give you the display labels for the scalar outputs.

Raises:

• ValueError: In case of invalid user-provided arguments.

to_json

to_json(**kwargs)

Returns a JSON string containing the network configuration.

To load a network from a JSON save file, use keras.models.model_from_json(json_string, custom_objects={}).

Arguments:

• **kwargs: Additional keyword arguments to be passed to json.dumps().

Returns:

A JSON string.

to_yaml

to_yaml(**kwargs)

Returns a yaml string containing the network configuration.

To load a network from a yaml save file, use keras.models.model_from_yaml(yaml_string, custom_objects={}).

custom_objects should be a dictionary mapping the names of custom losses / layers / etc to the corresponding functions / classes.

Arguments:

• **kwargs: Additional keyword arguments to be passed to yaml.dump().

Returns:

A YAML string.

Raises:

• ImportError: if yaml module is not found.

train_on_batch

train_on_batch(
    x,
    y,
    sample_weight=None,
    class_weight=None
)

Runs a single gradient update on a single batch of data.

Arguments:

• x: Numpy array of training data, or list of Numpy arrays if the model has multiple inputs. If all inputs in the model are named, you can also pass a dictionary mapping input names to Numpy arrays.
• y: Numpy array of target data, or list of Numpy arrays if the model has multiple outputs. If all outputs in the model are named, you can also pass a dictionary mapping output names to Numpy arrays.
• sample_weight: Optional array of the same length as x, containing weights to apply to the model's loss for each sample. In the case of temporal data, you can pass a 2D array with shape (samples, sequence_length), to apply a different weight to every timestep of every sample. In this case you should make sure to specify sample_weight_mode="temporal" in compile().
• class_weight: Optional dictionary mapping class indices (integers) to a weight (float) to apply to the model's loss for the samples from this class during training. This can be useful to tell the model to "pay more attention" to samples from an under-represented class.

Returns:

Scalar training loss (if the model has a single output and no metrics) or list of scalars (if the model has multiple outputs and/or metrics). The attribute model.metrics_names will give you the display labels for the scalar outputs.

Raises:

• ValueError: In case of invalid user-provided arguments.