[Python] Tensorflow: Getting scalar tensor value as int for pass to set_shape()

I'm attempting to load 3D images and their labels from a numpy array to TensorFlow records, then read them from a queue while training my network. The code for conversion is based on the conversion for TensorFlow's Inception model.

Each image has a different height, width, and depth value, so when reshaping the array I need to know these values. However, I'm getting an error when I try to use set_shape, as somewhere down the line int() is being used, and it doesn't accept Tensor values.

reader = tf.TFRecordReader()
_, value = reader.read(filename_queue)


# Features in Example proto
feature_map = {
'height': tf.VarLenFeature(dtype=tf.int64),
'width': tf.VarLenFeature(dtype=tf.int64),
'depth': tf.VarLenFeature(dtype=tf.int64),
'label': tf.VarLenFeature(dtype=tf.int64),
'image_raw': tf.VarLenFeature(dtype=tf.string)
}

features = tf.parse_single_example(value, feature_map)
result.label = tf.cast(features['label'].values[0], dtype=tf.int32)
result.height = tf.cast(features['height'].values[0], dtype=tf.int32)
result.width = tf.cast(features['width'].values[0], dtype=tf.int32)
result.depth = tf.cast(features['depth'].values[0], dtype=tf.int32)

image = tf.decode_raw(features['image_raw'].values[0], tf.int16)

image = tf.reshape(image, [result.depth, result.height, result.width])
image = tf.cast(tf.transpose(image, [1, 2, 0]), tf.float32)
result.image = tf.expand_dims(image, 3)

result.image.set_shape([result.height, result.width, result.depth, 1])
result.label = tf.expand_dims(result.label, 0)
result.label.set_shape([1])


Error trace:

Traceback (most recent call last):
File "dsb17_multi_gpu_train.py", line 227, in <module>
tf.app.run()
File "/usr/local/lib/python3.4/dist-packages/tensorflow/python/platform/app.py", line 44, in run
_sys.exit(main(_sys.argv[:1] + flags_passthrough))
File "dsb17_multi_gpu_train.py", line 223, in main
train()
File "dsb17_multi_gpu_train.py", line 129, in train
loss = tower_loss(scope)
File "dsb17_multi_gpu_train.py", line 34, in tower_loss
images, labels = dsb17.inputs(False)
File "/home/ubuntu/dsb17/model/dsb17.py", line 104, in inputs
batch_size=FLAGS.batch_size)
File "/home/ubuntu/dsb17/model/dsb17_input.py", line 161, in inputs
read_input = read_data(filename_queue)
File "/home/ubuntu/dsb17/model/dsb17_input.py", line 62, in read_data
result.image.set_shape([result.height, result.width, result.depth, 1])
File "/usr/local/lib/python3.4/dist-packages/tensorflow/python/framework/ops.py", line 425, in set_shape
self._shape = self._shape.merge_with(shape)
File "/usr/local/lib/python3.4/dist-packages/tensorflow/python/framework/tensor_shape.py", line 573, in merge_with
other = as_shape(other)
File "/usr/local/lib/python3.4/dist-packages/tensorflow/python/framework/tensor_shape.py", line 821, in as_shape
return TensorShape(shape)
File "/usr/local/lib/python3.4/dist-packages/tensorflow/python/framework/tensor_shape.py", line 457, in __init__
self._dims = [as_dimension(d) for d in dims_iter]
File "/usr/local/lib/python3.4/dist-packages/tensorflow/python/framework/tensor_shape.py", line 457, in <listcomp>
self._dims = [as_dimension(d) for d in dims_iter]
File "/usr/local/lib/python3.4/dist-packages/tensorflow/python/framework/tensor_shape.py", line 378, in as_dimension
return Dimension(value)
File "/usr/local/lib/python3.4/dist-packages/tensorflow/python/framework/tensor_shape.py", line 33, in __init__
self._value = int(value)
TypeError: int() argument must be a string, a bytes-like object or a number, not 'Tensor'


I originally thought this was because the Tensor did not have a value until it was evaluated in a session, but loss is being evaluated in a sess.run(), which is what requires the call to tower_loss(). My training code is identical in structure to cifar10_multi_gpu_train.py, and the overall file structure is also very similar.

The question then is: Is it actually being evaluated in a session, or is the graph not built yet? Do I need to somehow extract a value from the zero-dimensional Tensor? More generally, what am I misunderstanding about Tensors and sessions that is making my code not work as I expect it to?

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