python None object : <p>could you please explain what do I get in python with this lines? What does this code creates?</p>

<pre><code> NP = 2
 NB = 2  
 ND = 2 

 N  = NP*NB*ND 
 M  = 2*N + NP*NB
 res =  [[None] * 3] * (M)
</code></pre>

<p>Thanks in advance!</p>
