title: Initializing tf.Variable from a Tensor Object (not a tf.Variable)
body: <p>I'm trying to initialize a <code>tf.Variable</code> from a tensor object. Normally, from another <code>tf.Variable</code> you simply just used the <code>initialized_value()</code> but if you make a tensor object this does not work:</p>
  
  <pre><code>a = tf.constant([4,5,6])
  b = tf.Variable(a.initialized_value())
  </code></pre>
  
  <p>I have tried <code>b = tf.Variable(a)</code> but upon <code>initialize_all_variables()</code> being ran, tensorflow asks for a placeholder to be filled which is not correct. </p>
  
  <p>The reason why I'm doing this in the first place is that @mrry has suggested to place a tf.Variable into the params argument in <code>tf.gather</code> to help speed things up. </p>
  
  <p>Thanks for your feedback!</p>