title: Generating dates for unique combination of data
body: <p>relatively new to Python. I'm trying to generate a date column for each unique combination of data in my dataframe. For instance, in this example I just want 3 days of data for each row -</p>
  <p>Input:</p>
  <pre><code>  a      |      b      |      c      |      d     
    dogs          15           brown         30
    cats          24           black         43
  </code></pre>
  <p>Ideal output:</p>
  <pre><code>date      |     a      |      b      |      c      |      d     
  day 1           dogs          15           brown         30
  day 2           dogs          15           brown         30
  day 3           dogs          15           brown         30
  day 1           dogs          24           black         43
  day 2           dogs          24           black         43
  day 3           dogs          24           black         43
  </code></pre>
  <p>In my actual dataset, I need roughly 2 years of data per row, but ideally that's a variable that I can input somewhere in case someday I wanted 4/5 years of data. Any suggestions?</p>