title: TypeError: unsupported operand type(s) for -: 'list' and 'list'
body: <p>I am trying to implement the Naive Gauss and getting the unsupported operand type error on execution.
  Output:</p>
  
  <pre><code>  execfile(filename, namespace)
    File "/media/zax/MYLINUXLIVE/A0N-.py", line 26, in &lt;module&gt;
      print Naive_Gauss([[2,3],[4,5]],[[6],[7]])
    File "/media/zax/MYLINUXLIVE/A0N-.py", line 20, in Naive_Gauss
      b[row] = b[row]-xmult*b[column]
  TypeError: unsupported operand type(s) for -: 'list' and 'list'
  &gt;&gt;&gt;   
  </code></pre>
  
  <p>This is the code</p>
  
  <pre><code>def Naive_Gauss(Array,b):
      n = len(Array)
  
      for column in xrange(n-1):
          for row in xrange(column+1, n):
              xmult = Array[row][column] / Array[column][column]
              Array[row][column] = xmult
              #print Array[row][col]
              for col in xrange(0, n):
                  Array[row][col] = Array[row][col] - xmult*Array[column][col]
              b[row] = b[row]-xmult*b[column]
  
  
      print Array
      print b
  
  print Naive_Gauss([[2,3],[4,5]],[[6],[7]])
  </code></pre>