>>> import albatross
>>> ctx = albatross.SimpleContext('.')
>>> albatross.Template(ctx, '<magic>', '''
... <al-for iter="i" expr="range(15)" cols="4" flow="across">
...  <al-for iter="c" expr="i.value()">
...   <al-value expr="' %2d' % c.value()">
...  </al-for whitespace>
... </al-for>
... ''').to_html(ctx)
>>> ctx.flush_content()
  0  1  2  3
  4  5  6  7
  8  9 10 11
 12 13 14