title: Use of None in Array indexing in Python
body: <p>I am using the LSTM tutorial for Theano (<a href="http://deeplearning.net/tutorial/lstm.html">http://deeplearning.net/tutorial/lstm.html</a>). In the lstm.py (<a href="http://deeplearning.net/tutorial/code/lstm.py">http://deeplearning.net/tutorial/code/lstm.py</a>) file, I don't understand the following line:</p>
  
  <pre><code>c = m_[:, None] * c + (1. - m_)[:, None] * c_
  </code></pre>
  
  <p>What does <code>m_[:, None]</code> mean? In this case <code>m_</code> is the theano vector while <code>c</code> is a matrix.</p>