title: Comparing pandas Series for equality when they contain nan?
body: <p>My application needs to compare Series instances that sometimes contain nans. That causes ordinary comparison using <code>==</code> to fail, since <code>nan != nan</code>:</p>
  
  <pre><code>import numpy as np
  from pandas import Series
  s1 = Series([1,np.nan])
  s2 = Series([1,np.nan])
  
  &gt;&gt;&gt; (Series([1, nan]) == Series([1, nan])).all()
  False
  </code></pre>
  
  <p>What's the proper way to compare such Series?</p>