title: How to manage .unstack() ValueError by adding a number a after a duplicate
body: <p>I know it seem similar to other question, but I can't find the solution on the link someone marked this question as duplicate. Maybe someone can explain. So here we are. I have a dataset (<code>df</code>) of time series as follow:</p>
  
  <pre><code>date          symbol    close
  09/01/2018    ACA       132,1
  10/01/2018    ACA       134,4
  ...
  28/04/2013    BA        22,12
  ...
  21/01/2016    DIL       180,01
  ...
  </code></pre>
  
  <p>The idea was to convert it as this:</p>
  
  <pre><code>date          ACA        BA        DIL
  28/04/2013    NaN        22,12     NaN
  ...
  21/01/2016    NaN        23        180,01
  ...
  ...
  ...
  10/01/2018    134,4      32,2      181,3
  </code></pre>
  
  <p>As suggested by <a href="https://stackoverflow.com/a/49957768/8981559">Troy D</a> It can be used <code>df.unstack()</code> as follow:</p>
  
  <pre><code>df = df.set_index(['date', 'symbol'])
  df = df.unstack()
  df = df['close']
  </code></pre>
  
  <p>The problem is that I sometimes have multiple time series with the same "symbol". Therefore, if I do nothing this error appears:</p>
  
  <blockquote>
    <p>ValueError: Index contains duplicate entries, cannot reshape</p>
  </blockquote>
  
  <p>Since I don't want them to be merged, how could I rename them following, for example, by 2,3, and so on to make easier to <code>unstack()</code>?</p>