title: h5py - Get Index of Specific Values
body: <p>I have an .h5 file that is being read in python via the h5py library. Code to pull in the data is:</p>
  
  <pre><code>file = h5py.File('example.h5','r+')
  data_file = file['data_1'] 
  dates = data_file['Date']
  </code></pre>
  
  <p>I would like to get a list of the index values for a specific date. For example, The dates dataset has ~300 values (out of 10K) that are 20120304. Is there a way to get these index values without reading the entire dataset into memory? My end goal is to pull in all data where the dates row is equal to 20120304. </p>