modernize Python in losses.py and its tests

tensorflow/python/keras/losses.py

@@ -13,15 +13,10 @@
 # limitations under the License.
 # ==============================================================================
 """Built-in loss functions."""
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
 
 import abc
 import functools
 
-import six
-
 from tensorflow.python.autograph.core import ag_ctx
 from tensorflow.python.autograph.impl import api as autograph
 from tensorflow.python.distribute import distribution_strategy_context
@@ -50,7 +45,7 @@
 
 
 @keras_export('keras.losses.Loss')
-class Loss(object):
+class Loss:
   """Loss base class.
 
   To be implemented by subclasses:
@@ -241,7 +236,7 @@ def __init__(self,
       name: (Optional) name for the loss.
       **kwargs: The keyword arguments that are passed on to `fn`.
     """
-    super(LossFunctionWrapper, self).__init__(reduction=reduction, name=name)
+    super().__init__(reduction=reduction, name=name)
     self.fn = fn
     self._fn_kwargs = kwargs
 
@@ -263,9 +258,9 @@ def call(self, y_true, y_pred):
 
   def get_config(self):
     config = {}
-    for k, v in six.iteritems(self._fn_kwargs):
+    for k, v in self._fn_kwargs.items():
       config[k] = K.eval(v) if tf_utils.is_tensor_or_variable(v) else v
-    base_config = super(LossFunctionWrapper, self).get_config()
+    base_config = super().get_config()
     return dict(list(base_config.items()) + list(config.items()))
 
 
@@ -324,8 +319,7 @@ def __init__(self,
             more details.
       name: Optional name for the op. Defaults to 'mean_squared_error'.
     """
-    super(MeanSquaredError, self).__init__(
-        mean_squared_error, name=name, reduction=reduction)
+    super().__init__(mean_squared_error, name=name, reduction=reduction)
 
 
 @keras_export('keras.losses.MeanAbsoluteError')
@@ -383,8 +377,7 @@ def __init__(self,
             more details.
       name: Optional name for the op. Defaults to 'mean_absolute_error'.
     """
-    super(MeanAbsoluteError, self).__init__(
-        mean_absolute_error, name=name, reduction=reduction)
+    super().__init__(mean_absolute_error, name=name, reduction=reduction)
 
 
 @keras_export('keras.losses.MeanAbsolutePercentageError')
@@ -444,7 +437,7 @@ def __init__(self,
       name: Optional name for the op. Defaults to
         'mean_absolute_percentage_error'.
     """
-    super(MeanAbsolutePercentageError, self).__init__(
+    super().__init__(
         mean_absolute_percentage_error, name=name, reduction=reduction)
 
 
@@ -505,7 +498,7 @@ def __init__(self,
       name: Optional name for the op. Defaults to
         'mean_squared_logarithmic_error'.
     """
-    super(MeanSquaredLogarithmicError, self).__init__(
+    super().__init__(
         mean_squared_logarithmic_error, name=name, reduction=reduction)
 
 
@@ -599,7 +592,7 @@ def __init__(self,
             more details.
       name: (Optional) Name for the op. Defaults to 'binary_crossentropy'.
     """
-    super(BinaryCrossentropy, self).__init__(
+    super().__init__(
         binary_crossentropy,
         name=name,
         reduction=reduction,
@@ -678,7 +671,7 @@ def __init__(self,
             more details.
       name: Optional name for the op. Defaults to 'categorical_crossentropy'.
     """
-    super(CategoricalCrossentropy, self).__init__(
+    super().__init__(
         categorical_crossentropy,
         name=name,
         reduction=reduction,
@@ -755,7 +748,7 @@ def __init__(self,
       name: Optional name for the op. Defaults to
         'sparse_categorical_crossentropy'.
     """
-    super(SparseCategoricalCrossentropy, self).__init__(
+    super().__init__(
         sparse_categorical_crossentropy,
         name=name,
         reduction=reduction,
@@ -818,7 +811,7 @@ def __init__(self, reduction=losses_utils.ReductionV2.AUTO, name='hinge'):
             more details.
       name: Optional name for the op. Defaults to 'hinge'.
     """
-    super(Hinge, self).__init__(hinge, name=name, reduction=reduction)
+    super().__init__(hinge, name=name, reduction=reduction)
 
 
 @keras_export('keras.losses.SquaredHinge')
@@ -879,8 +872,7 @@ def __init__(self,
             more details.
       name: Optional name for the op. Defaults to 'squared_hinge'.
     """
-    super(SquaredHinge, self).__init__(
-        squared_hinge, name=name, reduction=reduction)
+    super().__init__(squared_hinge, name=name, reduction=reduction)
 
 
 @keras_export('keras.losses.CategoricalHinge')
@@ -939,8 +931,7 @@ def __init__(self,
             more details.
       name: Optional name for the op. Defaults to 'categorical_hinge'.
     """
-    super(CategoricalHinge, self).__init__(
-        categorical_hinge, name=name, reduction=reduction)
+    super().__init__(categorical_hinge, name=name, reduction=reduction)
 
 
 @keras_export('keras.losses.Poisson')
@@ -996,7 +987,7 @@ def __init__(self, reduction=losses_utils.ReductionV2.AUTO, name='poisson'):
             more details.
       name: Optional name for the op. Defaults to 'poisson'.
     """
-    super(Poisson, self).__init__(poisson, name=name, reduction=reduction)
+    super().__init__(poisson, name=name, reduction=reduction)
 
 
 @keras_export('keras.losses.LogCosh')
@@ -1053,7 +1044,7 @@ def __init__(self, reduction=losses_utils.ReductionV2.AUTO, name='log_cosh'):
             more details.
       name: Optional name for the op. Defaults to 'log_cosh'.
     """
-    super(LogCosh, self).__init__(log_cosh, name=name, reduction=reduction)
+    super().__init__(log_cosh, name=name, reduction=reduction)
 
 
 @keras_export('keras.losses.KLDivergence')
@@ -1113,8 +1104,7 @@ def __init__(self,
             more details.
       name: Optional name for the op. Defaults to 'kl_divergence'.
     """
-    super(KLDivergence, self).__init__(
-        kl_divergence, name=name, reduction=reduction)
+    super().__init__(kl_divergence, name=name, reduction=reduction)
 
 
 @keras_export('keras.losses.Huber')
@@ -1181,8 +1171,7 @@ def __init__(self,
             more details.
       name: Optional name for the op. Defaults to 'huber_loss'.
     """
-    super(Huber, self).__init__(
-        huber, name=name, reduction=reduction, delta=delta)
+    super().__init__(huber, name=name, reduction=reduction, delta=delta)
 
 
 @keras_export('keras.metrics.mean_squared_error', 'keras.metrics.mse',
@@ -1952,7 +1941,7 @@ def __init__(self,
                axis=-1,
                reduction=losses_utils.ReductionV2.AUTO,
                name='cosine_similarity'):
-    super(CosineSimilarity, self).__init__(
+    super().__init__(
         cosine_similarity, reduction=reduction, name=name, axis=axis)
 
 
@@ -2046,16 +2035,12 @@ def get(identifier):
   """
   if identifier is None:
     return None
-  if isinstance(identifier, six.string_types):
-    identifier = str(identifier)
-    return deserialize(identifier)
-  if isinstance(identifier, dict):
+  if isinstance(identifier, str) or isinstance(identifier, dict):
     return deserialize(identifier)
-  elif callable(identifier):
+  if callable(identifier):
     return identifier
-  else:
-    raise ValueError(
-        'Could not interpret loss function identifier: {}'.format(identifier))
+  raise ValueError(
+      f'Could not interpret loss function identifier: {identifier}')
 
 
 LABEL_DTYPES_FOR_LOSSES = {

tensorflow/python/keras/losses_test.py

@@ -14,10 +14,6 @@
 # ==============================================================================
 """Tests for Keras loss functions."""
 
-from __future__ import absolute_import
-from __future__ import division
-from __future__ import print_function
-
 from absl.testing import parameterized
 import numpy as np
 
@@ -1787,7 +1783,7 @@ def test_loss_with_non_default_dtype(self):
 class BinaryTruePositivesViaControlFlow(losses.Loss):
 
   def __init__(self, reduction=losses_utils.ReductionV2.AUTO):
-    super(BinaryTruePositivesViaControlFlow, self).__init__(reduction=reduction)
+    super().__init__(reduction=reduction)
 
   def call(self, y_true, y_pred):
     y_true = math_ops.cast(y_true, dtypes.bool)