Breaking down the attention API PR: part 2 (#11140)

### Summary

This refactoring will allow the simplification of some code in #8296

### Related Issues

### PR Overview

- [ ] This PR requires new unit tests [y/n] (make sure tests are included)
- [ ] This PR requires to update the documentation [y/n] (make sure the docs are up-to-date)
- [x] This PR is backwards compatible [y/n]
- [ ] This PR changes the current API [y/n] (all API changes need to be approved by fchollet)

Author: gabrieldemarmiesse

keras/engine/network.py

@@ -139,14 +139,8 @@ def _base_init(self, name=None):
     def _init_graph_network(self, inputs, outputs, name=None):
         self._uses_inputs_arg = True
         # Normalize and set self.inputs, self.outputs.
-        if isinstance(inputs, (list, tuple)):
-            self.inputs = list(inputs)  # Tensor or list of tensors.
-        else:
-            self.inputs = [inputs]
-        if isinstance(outputs, (list, tuple)):
-            self.outputs = list(outputs)
-        else:
-            self.outputs = [outputs]
+        self.inputs = to_list(inputs, allow_tuple=True)
+        self.outputs = to_list(outputs, allow_tuple=True)
 
         # User-provided argument validation.
         # Check for redundancy in inputs.

keras/engine/training.py

@@ -596,10 +596,7 @@ def _set_inputs(self, inputs, outputs=None, training=None):
         self._feed_inputs = []
         self._feed_input_names = []
         self._feed_input_shapes = []
-        if isinstance(inputs, (list, tuple)):
-            inputs = list(inputs)
-        else:
-            inputs = [inputs]
+        inputs = to_list(inputs, allow_tuple=True)
 
         for i, v in enumerate(inputs):
             name = 'input_%d' % (i + 1)
@@ -633,10 +630,7 @@ def _set_inputs(self, inputs, outputs=None, training=None):
                 outputs = self.call(unpack_singleton(self.inputs), training=training)
             else:
                 outputs = self.call(unpack_singleton(self.inputs))
-        if isinstance(outputs, (list, tuple)):
-            outputs = list(outputs)
-        else:
-            outputs = [outputs]
+        outputs = to_list(outputs, allow_tuple=True)
         self.outputs = outputs
         self.output_names = [
             'output_%d' % (i + 1) for i in range(len(self.outputs))]
@@ -704,10 +698,7 @@ def _standardize_user_data(self, x,
                                          'You passed: y=' + str(y))
                 # Typecheck that all inputs are *either* value *or* symbolic.
                 if y is not None:
-                    if isinstance(y, (list, tuple)):
-                        all_inputs += list(y)
-                    else:
-                        all_inputs.append(y)
+                    all_inputs += to_list(y, allow_tuple=True)
                 if any(K.is_tensor(v) for v in all_inputs):
                     if not all(K.is_tensor(v) for v in all_inputs):
                         raise ValueError('Do not pass inputs that mix Numpy '
@@ -716,8 +707,7 @@ def _standardize_user_data(self, x,
                                          '; y=' + str(y))
 
                 # Handle target tensors if any passed.
-                if not isinstance(y, (list, tuple)):
-                    y = [y]
+                y = to_list(y, allow_tuple=True)
                 target_tensors = [v for v in y if K.is_tensor(v)]
                 if not target_tensors:
                     target_tensors = None

keras/layers/advanced_activations.py

@@ -13,6 +13,7 @@
 from ..engine.base_layer import InputSpec
 from .. import backend as K
 from ..legacy import interfaces
+from ..utils.generic_utils import to_list
 
 
 class LeakyReLU(Layer):
@@ -100,10 +101,8 @@ def __init__(self, alpha_initializer='zeros',
         self.alpha_constraint = constraints.get(alpha_constraint)
         if shared_axes is None:
             self.shared_axes = None
-        elif not isinstance(shared_axes, (list, tuple)):
-            self.shared_axes = [shared_axes]
         else:
-            self.shared_axes = list(shared_axes)
+            self.shared_axes = to_list(shared_axes, allow_tuple=True)
 
     def build(self, input_shape):
         param_shape = list(input_shape[1:])

keras/layers/convolutional_recurrent.py

@@ -21,6 +21,7 @@
 from ..legacy.layers import Recurrent, ConvRecurrent2D
 from .recurrent import RNN
 from ..utils.generic_utils import has_arg
+from ..utils.generic_utils import to_list
 from ..utils.generic_utils import transpose_shape
 
 
@@ -387,10 +388,7 @@ def step(inputs, states):
             output._uses_learning_phase = True
 
         if self.return_state:
-            if not isinstance(states, (list, tuple)):
-                states = [states]
-            else:
-                states = list(states)
+            states = to_list(states, allow_tuple=True)
             return [output] + states
         else:
             return output
@@ -443,8 +441,7 @@ def get_tuple_shape(nb_channels):
                 K.set_value(self.states[0],
                             np.zeros(get_tuple_shape(self.cell.state_size)))
         else:
-            if not isinstance(states, (list, tuple)):
-                states = [states]
+            states = to_list(states, allow_tuple=True)
             if len(states) != len(self.states):
                 raise ValueError('Layer ' + self.name + ' expects ' +
                                  str(len(self.states)) + ' states, '

keras/layers/embeddings.py

@@ -10,6 +10,7 @@
 from .. import constraints
 from ..engine.base_layer import Layer
 from ..legacy import interfaces
+from ..utils.generic_utils import to_list
 
 
 class Embedding(Layer):
@@ -117,10 +118,7 @@ def compute_output_shape(self, input_shape):
             return input_shape + (self.output_dim,)
         else:
             # input_length can be tuple if input is 3D or higher
-            if isinstance(self.input_length, (list, tuple)):
-                in_lens = list(self.input_length)
-            else:
-                in_lens = [self.input_length]
+            in_lens = to_list(self.input_length, allow_tuple=True)
             if len(in_lens) != len(input_shape) - 1:
                 raise ValueError('"input_length" is %s, but received input has shape %s' %
                                  (str(self.input_length), str(input_shape)))

keras/layers/recurrent.py

@@ -16,6 +16,7 @@
 from ..engine.base_layer import Layer
 from ..engine.base_layer import InputSpec
 from ..utils.generic_utils import has_arg
+from ..utils.generic_utils import to_list
 
 # Legacy support.
 from ..legacy.layers import Recurrent
@@ -664,10 +665,7 @@ def step(inputs, states):
                 state._uses_learning_phase = True
 
         if self.return_state:
-            if not isinstance(states, (list, tuple)):
-                states = [states]
-            else:
-                states = list(states)
+            states = to_list(states, allow_tuple=True)
             return [output] + states
         else:
             return output
@@ -702,8 +700,7 @@ def reset_states(self, states=None):
                 K.set_value(self.states[0],
                             np.zeros((batch_size, self.cell.state_size)))
         else:
-            if not isinstance(states, (list, tuple)):
-                states = [states]
+            states = to_list(states, allow_tuple=True)
             if len(states) != len(self.states):
                 raise ValueError('Layer ' + self.name + ' expects ' +
                                  str(len(self.states)) + ' states, '

keras/legacy/layers.py

@@ -508,8 +508,7 @@ def __call__(self, inputs, initial_state=None, **kwargs):
         if initial_state is None:
             return super(Recurrent, self).__call__(inputs, **kwargs)
 
-        if not isinstance(initial_state, (list, tuple)):
-            initial_state = [initial_state]
+        initial_state = to_list(initial_state, allow_tuple=True)
 
         is_keras_tensor = hasattr(initial_state[0], '_keras_history')
         for tensor in initial_state:
@@ -602,10 +601,7 @@ def call(self, inputs, mask=None, training=None, initial_state=None):
             output = last_output
 
         if self.return_state:
-            if not isinstance(states, (list, tuple)):
-                states = [states]
-            else:
-                states = list(states)
+            states = to_list(states, allow_tuple=True)
             return [output] + states
         else:
             return output
@@ -633,8 +629,7 @@ def reset_states(self, states=None):
             for state in self.states:
                 K.set_value(state, np.zeros((batch_size, self.units)))
         else:
-            if not isinstance(states, (list, tuple)):
-                states = [states]
+            states = to_list(states, allow_tuple=True)
             if len(states) != len(self.states):
                 raise ValueError('Layer ' + self.name + ' expects ' +
                                  str(len(self.states)) + ' states, '

keras/utils/generic_utils.py

@@ -444,20 +444,26 @@ def add(self, n, values=None):
         self.update(self._seen_so_far + n, values)
 
 
-def to_list(x):
+def to_list(x, allow_tuple=False):
     """Normalizes a list/tensor into a list.
 
     If a tensor is passed, we return
     a list of size 1 containing the tensor.
 
     # Arguments
         x: target object to be normalized.
+        allow_tuple: If False and x is a tuple,
+            it will be converted into a list
+            with a single element (the tuple).
+            Else converts the tuple to a list.
 
     # Returns
         A list.
     """
     if isinstance(x, list):
         return x
+    if allow_tuple and isinstance(x, tuple):
+        return list(x)
     return [x]
 
 
@@ -483,10 +489,7 @@ def object_list_uid(object_list):
 
 
 def is_all_none(iterable_or_element):
-    if not isinstance(iterable_or_element, (list, tuple)):
-        iterable = [iterable_or_element]
-    else:
-        iterable = iterable_or_element
+    iterable = to_list(iterable_or_element, allow_tuple=True)
     for element in iterable:
         if element is not None:
             return False