How to get the dimensions of a tensor (in TensorFlow) at graph construction time?

Just print out the embed after construction graph (ops) without running:

import tensorflow as tf

...

train_dataset = tf.placeholder(tf.int32, shape=[128, 2])
embeddings = tf.Variable(
    tf.random_uniform([50000, 64], -1.0, 1.0))
embed = tf.nn.embedding_lookup(embeddings, train_dataset)
print (embed)

This will show the shape of the embed tensor:

Tensor("embedding_lookup:0", shape=(128, 2, 64), dtype=float32)

Usually, it’s good to check shapes of all tensors before training your models.

A function to access the values:

def shape(tensor):
    s = tensor.get_shape()
    return tuple([s[i].value for i in range(0, len(s))])

Example:

batch_size, num_feats = shape(logits)

I see most people confused about tf.shape(tensor) and tensor.get_shape()
Let’s make it clear:

1. tf.shape

tf.shape is used for dynamic shape. If your tensor’s shape is changable, use it.
An example: a input is an image with changable width and height, we want resize it to half of its size, then we can write something like:
new_height = tf.shape(image)[0] / 2

2. tensor.get_shape

tensor.get_shape is used for fixed shapes, which means the tensor’s shape can be deduced in the graph.

Conclusion:
tf.shape can be used almost anywhere, but t.get_shape only for shapes can be deduced from graph.

Let’s make it simple as hell. If you want a single number for the number of dimensions like 2, 3, 4, etc., then just use tf.rank(). But, if you want the exact shape of the tensor then use tensor.get_shape()

with tf.Session() as sess:
   arr = tf.random_normal(shape=(10, 32, 32, 128))
   a = tf.random_gamma(shape=(3, 3, 1), alpha=0.1)
   print(sess.run([tf.rank(arr), tf.rank(a)]))
   print(arr.get_shape(), ", ", a.get_shape())     


# for tf.rank()    
[4, 3]

# for tf.get_shape()
Output: (10, 32, 32, 128) , (3, 3, 1)

The method tf.shape is a TensorFlow static method. However, there is also the method get_shape for the Tensor class. See

https://www.tensorflow.org/api_docs/python/tf/Tensor#get_shape

To create tensor in tensorflow using tf.constant()

This is to import the library

import tensorflow as tf

This will create the tensor

tensor = tf.constant([[[2,4,5], [5,6,6]], [[9,7,8], [4,8,2]], [[7,1,3], [4,8,9]]])

This will show the tensor

tensor

this will show the number of dimension

tensor.ndim

#create a tensor

tensor = tf.constant([[[1, 2, 3],
                   [3, 4, 5]],
                  [[5, 6, 7],
                   [8, 6, 9]],
                  [[2, 1, 5],
                   [5, 7, 8]]])
tensor

#Display result

<tf.Tensor: shape=(3, 2, 3), dtype=int32, numpy= array([[[1, 2, 3],[3, 4, 5]],

   [[5, 6, 7],
    [8, 6, 9]],

   [[2, 1, 5],
    [5, 7, 8]]], dtype=int32)>