title: How to add a single item to a Pandas Series
body: <p>How do I add a single item to a Pandas <code>Series</code> instance?</p>
  <p>I'm looking for code along the lines of</p>
  <pre><code>&gt;&gt;&gt; x = Series()
  &gt;&gt;&gt; N = 4
  &gt;&gt;&gt; for i in xrange(N):
  &gt;&gt;&gt;     x.some_appending_function(i**2)    
  &gt;&gt;&gt; print(x)
  0 | 0
  1 | 1
  2 | 4
  3 | 9
  </code></pre>
  <p>Similarly, how can i add a single row to a Pandas <code>DataFrame</code>?</p>