title: How do I fill a column with one value in Pandas?
body: <p>I have a column with consecutive digits in a Pandas DataFrame.</p>
  
  <pre><code>A
  1
  2
  3
  4
  </code></pre>
  
  <p>I would like to change all those values to a simple string, say "foo", resulting in</p>
  
  <pre><code>A
  foo
  foo
  foo
  foo
  </code></pre>