title: How can I find the square matrix of a lower triangular numpy matrix? (with a rotated upper triangle)
body: <p>I generated a lower triangular matrix, and I want to complete the matrix using the values in the lower triangular matrix to form a square matrix.</p>
  
  <pre><code>    lower_triangle = numpy.array([
      [0,0,0,0],
      [1,0,0,0],
      [2,3,0,0],
      [4,5,6,0]])
  </code></pre>
  
  <p>I want to generate the following complete matrix, maintaining the zero diagonal:</p>
  
  <pre><code>    complete_matrix = numpy.array([
      [0, 6, 5, 4],
      [1, 0, 3, 2],
      [2, 3, 0, 1],
      [4, 5, 6, 0]])
  </code></pre>
  
  <p>Thanks.</p>