How to assign a value to a TensorFlow variable?

Question

I am trying to assign a new value to a tensorflow variable in python.

import tensorflow as tf import numpy as np  x = tf.Variable(0) init = tf.initialize_all_variables() sess = tf.InteractiveSession() sess.run(init)  print(x.eval())  x.assign(1) print(x.eval()) 

But the output I get is

0 0 

So the value has not changed. What am I missing?

Answer 1

In TF1, the statement x.assign(1) does not actually assign the value 1 to x, but rather creates a tf.Operation that you have to explicitly run to update the variable.* A call to Operation.run() or Session.run() can be used to run the operation:

assign_op = x.assign(1) sess.run(assign_op)  # or `assign_op.op.run()` print(x.eval()) # ==> 1 

(* In fact, it returns a tf.Tensor, corresponding to the updated value of the variable, to make it easier to chain assignments.)

However, in TF2 x.assign(1) will now assign the value eagerly:

x.assign(1) print(x.numpy()) # ==> 1