title: Python pandas equivalent for replace
body: <p>In R, there is a rather useful <code>replace</code> function.
  Essentially, it does conditional re-assignment in a given column of a data frame.
  It can be used as so:
  <code>replace(df$column, df$column==1,'Type 1');</code></p>
  
  <p>What is a good way to achieve the same in pandas?</p>
  
  <p>Should I use a lambda with <code>apply</code>? (If so, how do I get a reference to the given column, as opposed to a whole row).</p>
  
  <p>Should I use <code>np.where</code> on <code>data_frame.values</code>?
  It seems like I am missing a very obvious thing here.</p>
  
  <p>Any suggestions are appreciated.</p>