title: Extract values array using indices
body: <p>I need to extract certain values from a multidimensional array that are not subsequent.</p>
  
  <pre><code>import numpy as np    
  A = np.array([[[ 0.,          4.,          0.        ],
                 [ 0.19230769,  4.03846154,  0.        ],
                 [-0.4,         4.8,         0.        ],
                 [ 2.,          1.,          0.        ]],
  
                [[ 1.2,         3.4,         0.        ],
                 [ 2.11538462,  4.42307692,  0.        ],
                 [ 0.,          4.,          0.        ],
                 [ 3.6,         1.8,         0.        ]],
  
                [[ 1.8,         3.1,         0.        ],
                 [ 3.17307692,  4.63461538,  0.        ],
                 [ 0.,          4.,          0.        ],
                 [ 4.,          2.,          0.        ]]])
  </code></pre>
  
  <p>For every 4x3 block I want to extract an arbitrary row</p>
  
  <p>For instance the following elements:</p>
  
  <pre><code>A[0,2,:]
  A[1,1,:]
  A[2,1,:]
  </code></pre>
  
  <p>So basicly the rows<code>B = [2,1,1]</code>, which would give me:</p>
  
  <pre><code>[-0.4         4.8         0.        ]
  [ 2.11538462  4.42307692  0.        ]
  [ 3.17307692  4.63461538  0.        ]
  </code></pre>
  
  <p>How to do this efficiently?</p>