using a `tf.Tensor` as a Python `bool` is not allowed in Graph execution. Use Eager execution or decorate this function with @tf.function

Question

Currently I faced this error, can anyone help solve it?

---------------------------------------------------------------------------
OperatorNotAllowedInGraphError            Traceback (most recent call last)
<ipython-input-24-0211c82920d0> in <module>
      7 warnings.filterwarnings("ignore")
      8 model.train(dataset_train,dataset_val, learning_rate=config.LEARNING_RATE,epochs=5,
----> 9             layers='heads')
/kaggle/working/maskrcnn/Mask_RCNN-master/mrcnn/model.py in train(self, train_dataset, val_dataset, learning_rate, epochs, layers, augmentation, custom_callbacks, no_augmentation_sources)
   2355         log("Checkpoint Path: {}".format(self.checkpoint_path))
   2356         self.set_trainable(layers)
-> 2357         self.compile(learning_rate, self.config.LEARNING_MOMENTUM)
   2358
   2359         # Work-around for Windows: Keras fails on Windows when using
/kaggle/working/maskrcnn/Mask_RCNN-master/mrcnn/model.py in compile(self, learning_rate, momentum)
   2168         for name in loss_names:
   2169             layer = self.keras_model.get_layer(name)
-> 2170             if layer.output in self.keras_model.losses:
   2171                 continue
   2172             loss = (
/opt/conda/lib/python3.6/site-packages/tensorflow_core/python/framework/ops.py in __bool__(self)
    763       `TypeError`.
    764     """
--> 765     self._disallow_bool_casting()
    766
    767   def __nonzero__(self):

/opt/conda/lib/python3.6/site-packages/tensorflow_core/python/framework/ops.py in _disallow_bool_casting(self)
    532     else:
    533       # Default: V1-style Graph execution.
--> 534       self._disallow_in_graph_mode("using a `tf.Tensor` as a Python `bool`")
    535
    536   def _disallow_iteration(self):

/opt/conda/lib/python3.6/site-packages/tensorflow_core/python/framework/ops.py in _disallow_in_graph_mode(self, task)
    521     raise errors.OperatorNotAllowedInGraphError(
    522         "{} is not allowed in Graph execution. Use Eager execution or decorate"
--> 523         " this function with @tf.function.".format(task))
    524
    525   def _disallow_bool_casting(self):

OperatorNotAllowedInGraphError: using a `tf.Tensor` as a Python `bool` is not allowed in Graph execution. Use Eager execution or decorate this function with @tf.function.

Answer 1

As the error message explain, you try to use a tf.Tensor as a Python bool. This happens generally where condition are expected like in:

if layer.output in self.keras_model.losses:

The part layer.output in self.keras_model.losses should evaluate to a tensor that Python try to use as a bool to check the if condition. This is allowed in eager execution only.

You must either convert the if construct with tf.cond, or rely on @tf.function to make the job for you.

Without more code, it is hard to help you more...