title: h5py symmetric array using pointers
body: <p>I've been looking for a way to create a custom h5py array that is in the end symmetric. Ideally it would be an array such that when it was created had a single value that <code>a[i][j]</code> and <code>a[j][i]</code> pointed to. The reason for this is that I will be writing a large distance vector into a square form matrix. The vector and square matrix are too large to hold in memory, so I would like a relatively fast solution to create the square matrix.</p>