How do I get the current value of a Variable?

Question

Suppose we have a variable:

x = tf.Variable(...) 

This variable can be updated during the training process using the assign() method.

What is the best way to get the current value of a variable?

I know we could use this:

session.run(x) 

But I'm afraid this would trigger a whole chain of operations.

In Theano, you could just do

y = theano.shared(...) y_vals = y.get_value() 

I'm looking for the equivalent thing in TensorFlow.

Answer 1

The only way to get the value of the variable is by running it in a session. In the FAQ it is written that:

A Tensor object is a symbolic handle to the result of an operation, but does not actually hold the values of the operation's output.

So TF equivalent would be:

import tensorflow as tf  x = tf.Variable([1.0, 2.0])  init = tf.global_variables_initializer()  with tf.Session() as sess:     sess.run(init)     v = sess.run(x)     print(v)  # will show you your variable. 

The part with init = global_variables_initializer() is important and should be done in order to initialize variables.

Also, take a look at InteractiveSession if you work in IPython.

Answer 2

In general, session.run(x) will evaluate only the nodes that are necessary to compute x and nothing else, so it should be relatively cheap if you want to inspect the value of the variable.

Take a look at this great answer https://stackoverflow.com/a/33610914/5543198 for more context.