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?
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