title: What is the most efficient way to search nested lists in python?
body: <p>I have a list that contains nested lists and I need to know the most efficient way to search within those nested lists.</p>
  
  <p>e.g., if I have </p>
  
  <pre><code>[['a','b','c'],
  ['d','e','f']]
  </code></pre>
  
  <p>and I have to search the entire list above, what is the most efficient way to find 'd'?</p>