Which is actually cleaner? (django templates)

gistfile1.txt

{% exec %}
try:
  f = durs[duration]
  f.field.widget.attrs['placeholder'] = duration
  print f
except KeyError:
  pass
{% endexec %}

OR

{% with durs|get:duration as f %}
  {% with "placeholder:"|add:duration as placeholder %}
    {{ f|attr:placeholder }}
  {% endwith %}
{% endwith %}