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)

實驗結果：

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

tensorflow使用assign（variable，new_value）來更改變數的值，但是真正作用在garph中，必須要呼叫gpu或者cpu執行這個更新過程。
session.run(update)
tensorflow不支援直接對變數進行賦值更改

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))

error:

"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