title: Fast way to localize time in python for large dataset?
body: <p>I have datetime objects as indices in a pandas dataframe that I would like to localize without using a for loop.  Here's the code: (data is the dataframe)</p>
  
  <pre><code>from pytz import timezone
  utc = timezone('UTC')
  utc_times = [utc.localize(entry) for entry in data.index]
  cst_times = [entry.astimezone(timezone('US/Central')) for entry in utc_times]
  data.index = cst_times
  </code></pre>
  
  <p>As the dataset grows, this gets slow.  Any ways to speed this up?</p>