title: How to slice a pandas.DataFrame?
body: <p>Here's a pd.Dataframe.</p>
  
  <pre><code>index date  state
  one   2000  Ohio
  two   2012  Ohio
  </code></pre>
  
  <p>And I want <code>df['state'] = 'California' where df['date'] == 2000 and df.index == one</code>.</p>
  
  <p>How can I do this?</p>
  
  <p>Thanks for the help!</p>