title: Pickling an object containing a large numpy array
body: <p>I'm pickling an object which has the following structure:</p>
  
  <pre><code>obj
    |---metadata
    |---large numpy array
  </code></pre>
  
  <p>I'd like to be able to access the metadata. However, if I pickle.load() the object and iterate over a directory (say because I'm looking for some specific metadata to determine which one to return), then it gets lenghty. I'm guessing pickle wants to load, well, the whole object.</p>
  
  <p>Is there a way to access only the top-level metadata of the object without having to load the whole thing?</p>
  
  <p>I thought about maintaining an index, but then it means I have to implement the logic of it and keep it current, which I'd rather avoid if there's an simpler solution....</p>