<a href="#Length_and_capacity"><code>len</code></a>; unlike with arrays it may change during
execution.  The elements can be addressed by integer <a href="#Index_expressions">indices</a>
0 through <code>len(s)-1</code>.  The slice index of a
given element may be less than the index of the same element in the
underlying array.
</p>
<p>
A slice, once initialized, is always associated with an underlying