title: Best way to determine if a sequence is in another sequence?
body: <p>This is a generalization of the "string contains substring" problem to (more) arbitrary types.</p>
  
  <p>Given an sequence (such as a list or tuple), what's the best way of determining whether another sequence is inside it?   As a bonus, it should return the index of the element where the subsequence starts:</p>
  
  <p>Example usage (Sequence in Sequence):</p>
  
  <pre><code>&gt;&gt;&gt; seq_in_seq([5,6],  [4,'a',3,5,6])
  3
  &gt;&gt;&gt; seq_in_seq([5,7],  [4,'a',3,5,6])
  -1 # or None, or whatever
  </code></pre>
  
  <p>So far, I just rely on brute force and it seems slow, ugly, and clumsy.</p>