title: Python does not recognize the type of a namedtuple
body: <p>I suspect this question has been asked before, but I have not been able to find it, so here goes:</p>
  
  <p>On Python (using 2.7) I create a <code>namedtuple</code> as below:</p>
  
  <pre><code>&gt;&gt;&gt; sgn_tuple = namedtuple('sgnt',['signal','type'])
  &gt;&gt;&gt; a = sgn_tuple("aaa","bbb")
  </code></pre>
  
  <p>Then I want to check the type of <code>t</code> and my results are weird:</p>
  
  <pre><code>&gt;&gt;&gt; type (a)
  &lt;class '__main__.sgnt'&gt;
  &gt;&gt;&gt; a is tuple
  False
  &gt;&gt;&gt; a is namedtuple
  False
  &gt;&gt;&gt; a is sgnt
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
  NameError: name 'sgnt' is not defined
  &gt;&gt;&gt; a is sgn_tuple
  False
  &gt;&gt;&gt;
  </code></pre>
  
  <p>Why is this so? I would expect <code>a</code> to be recognized as a tuple type, but it is not. Any hints?</p>