title: iPython query keys/shape/size in dictionary (whos for a dictionary)
body: <p>I am a new user of iPython. I frequently handle large datasets, loaded from (for example) netcdf files. I load the data into dictionaries and would like to be able to interactively query what keys are associated with the dictionary, their shape, datatypes, and how much size they occupy in memory.</p>
  
  <p>e.g., I have a dict called "dat", which has a number of keys associated with it:</p>
  
  <pre><code>In [21]: dat.keys()
  Out[21]: 
  ['Yp1',
   'diag_levels',
   'PHIHYD',
   'iter',
   'UVEL',
   'VVEL',
   'T',
   'THETA',
   'Y',
   'X',
   'Xp1',
   'WVEL',
   'RHOAnoma']
  </code></pre>
  
  <p>I know I could then query each key to get their shape using Numpy's</p>
  
  <pre><code>np.shape(dat['Yp1'])
  </code></pre>
  
  <p>But I'm wondering if there's a function that will just return it all nicely formatted in one go, something like "whos", but that will actually query the dictionary.</p>
  
  <p>Thanks for any help.</p>