title: How to understand constructor of tf.FIFOQueue?
body: <p>I have written some code, but I can't explain well.</p>
  
  <p>The first code:</p>
  
  <pre><code>import tensorflow as tf
  
  f = tf.FIFOQueue(10, [tf.int32, tf.int32])
  en = f.enqueue([[1,2],[3,4]])
  de = f.dequeue()
  with tf.Session() as sess:
      en.run()
      x = sess.run(de)
      print(x)
  </code></pre>
  
  <p>I define the element of queue is a tuple of tensor, so when I enqueue <code>[[1,2],[3,4]]</code>, it works well and the output is <code>[array([1, 2]), array([3, 4])]</code>.</p>
  
  <p>But the second code, I can't understand.</p>
  
  <pre><code>import tensorflow as tf
  
  f = tf.FIFOQueue(10, [tf.int32])
  en = f.enqueue([1,2,3,4])
  de = f.dequeue()
  with tf.Session() as sess:
      en.run()
      x = sess.run(de)
      print(x)
  </code></pre>
  
  <p>According to the first code, I think output is <code>[array(1, 2, 3, 4)]</code>, but in fact, the output is <code>1</code>. How to explain well for the second code?</p>