from __future__ import print_function,division
import tensorflow as tf

#create a Variable
w=tf.Variable(initial_value=[[1,2],[3,4]],dtype=tf.float32)
x=tf.Variable(initial_value=[[1,1],[1,1]],dtype=tf.float32,validate_shape=False)

init_op=tf.global_variables_initializer()
update=tf.assign(x,[[1,2],[1,2]])

with tf.Session() as session:
 session.run(init_op)
 session.run(update)
 x=session.run(x)
 print(x)

[[ 1. 2.]
 [ 1. 2.]]

from __future__ import print_function,division
import tensorflow as tf

#create a Variable
x=tf.Variable(initial_value=[[1,1],[1,1]],dtype=tf.float32,validate_shape=False)
x=[[1,3],[2,4]]
init_op=tf.global_variables_initializer()
update=tf.assign(x,[[1,2],[1,2]])
with tf.Session() as session:
 session.run(init_op)
 session.run(update)
 print(session.run(x))

"C:\Program Files\Anaconda3\python.exe" D:/pycharmprogram/tensorflow_learn/assign_learn/assign_learn.py
Traceback (most recent call last):
 File "D:/pycharmprogram/tensorflow_learn/assign_learn/assign_learn.py", line 8, in <module>
 update=tf.assign(x,[[1,2],[1,2]])
 File "C:\Program Files\Anaconda3\lib\site-packages\tensorflow\python\ops\state_ops.py", line 271, in assign
 if ref.dtype._is_ref_dtype:
AttributeError: 'list' object has no attribute 'dtype'

Process finished with exit code 1