title: Slicing a matrix with Python
body: <p>I need to slice 12*12 matrix to 24 2*3 pieces. Matrix of input is:</p>
  
  <pre><code>arr = [
  [1,0,1,1,1,0,1,1,1,0,1,0],
  [0,0,0,1,0,1,1,1,1,0,1,0],
  [0,1,1,0,0,0,1,0,1,0,0,0],
  [1,0,0,1,0,0,1,1,1,0,1,1],
  [0,0,0,1,0,0,0,1,1,1,1,0],
  [0,0,0,0,0,1,1,0,0,0,0,1],
  [1,0,1,0,0,0,1,1,0,0,1,1],
  [0,0,1,1,0,1,0,1,1,0,1,0],
  [0,1,0,0,0,0,1,0,1,0,0,1],
  [1,1,0,1,0,1,0,1,0,1,0,0],
  [0,0,1,1,1,1,0,1,0,1,1,1],
  [0,0,0,0,1,0,0,0,1,1,0,0]]
  </code></pre>
  
  <p>I try to achieve the task with numpy Matrix:</p>
  
  <pre><code>from sympy import Matrix
  Matrix(arr)[:3,:2]
  </code></pre>
  
  <p>But it will give only one slice from the original matrices.</p>
  
  <pre><code>Matrix([
  [1, 0],
  [0, 0],
  [0, 1]])
  </code></pre>
  
  <p>What is the convenient way to slice 12*12 matrices to 2*3 pieces? I also need to have dimensions 3*2 of the original, but suppose it's easy after getting the first one ready.</p>