Tensorflow,为变量赋值

Question

对于tensorflow,我是新手,我正在学习

https://www.tensorflow.org/get_started/get_started

fixW = tf.assign(W, [-1.])

工作正常,但是

fixb = tf.assign(b, [1.])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/milenko/anaconda3/lib/python3.6/site-packages/tensorflow/python/ops/state_ops.py", line 272, in assign
    return ref.assign(value)
AttributeError: 'Tensor' object has no attribute 'assign'

另一个例子

zero_tsr = tf.zeros([1.,2.])
zero_tsr
<tf.Tensor 'zeros:0' shape=(1, 2) dtype=float32>

如果我尝试更改zero_tsr

fixz = tf.assign(zero_tsr, [2.,2.])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/milenko/anaconda3/lib/python3.6/site-packages/tensorflow/python/ops/state_ops.py", line 272, in assign
    return ref.assign(value)
AttributeError: 'Tensor' object has no attribute 'assign'

同样,同样的问题.

我没有改变shell,一切都是一样的.为什么我这里有问题？

Answer 1

在您发布的示例中:

zero_tsr = tf.zeros([1.,2.])
zero_tsr
<tf.Tensor 'zeros:0' shape=(1, 2) dtype=float32>

zero_tsr 是常量而不是变量,因此您无法为其赋值.

从文档:

assign(ref,value,validate_shape = None,use_locking = None,name = None)

ref:一个可变的Tensor.应该来自一个Variable节点.可能是未初始化的.

例如,这将正常工作:

import tensorflow as tf
zero_tsr = tf.Variable([0,0])
tf.assign(zero_tsr,[4,5])

而这段代码会引发错误

import tensorflow as tf
zero_tsr = tf.zeros([1,2])
tf.assign(zero_tsr,[4,5])

引发的错误正是您发布的错误:

AttributeError:'Tensor'对象没有属性'assign'