title: Concatenate two or more variables using Pandas to create a new variable
body: <p>Input dataset:</p>
  
  <pre><code>Var1     Var2   Var3    Var4
  
  101 XXX       yyyy   12/10/2014
  
  101  XYZ      YTRT  13/10/2014
  
  102  TTY       UUUU  9/9/2014
  
  102  YTY      IUYY   10/10/2014
  </code></pre>
  
  <p>Expected dataset:</p>
  
  <pre><code>Var1     Var2   Var3    Var4         New_Variable
  
  101 XXX       yyyy   12/10/2014       XXX, yyyy
  
  101  XYZ      YTRT  13/10/2014        XYZ, YTRT
  
  102  TTY       UUUU  9/9/2014         TTY, UUUU
  
  102  YTY      IUYY   10/10/2014       YTY, IUYY
  </code></pre>
  
  <p>How can I concatenate two or more string variables and create a new variable capturing the concatenated values in the same dataset?</p>