title: store a matrix (or a 2D array)as values for each key in a dictionary
body: <p>I have the following table coming from SQL:</p>
  
  <pre><code>b_num   loc max_neg_m   
  10    0.89  -480050 
  10    0.93  -144107 
  10    0.96  -364381 
  10    1     -699219 
  100   0     -904713 
  100   0.2   -772981 
  100   0.41  -645617 
  100   0.5   -563448 
  100   0.67  -520747 
  100   1     -218334 
  1000  0     -112367 
  1000  0.05  15976   
  </code></pre>
  
  <p>with a python code, I'm looking to store a 2D array of loc, max_neg_m for each unique b_num. </p>
  
  <pre><code>a=dict()
  
  a.keys(b_num)
  
  a.values=[loc,max_neg_m]
  </code></pre>
  
  <p>I appreciate any help.</p>