title: How to split value column and append it into dataframe pandas?
body: <p><strong>Example Problem</strong></p>
  <pre><code>df =
         variant    variant_param    variant_new
    0        car    petro / young            Nan
    1       bike     fred / trail            NaN
    2     bottle              Nan            NaN
  </code></pre>
  <p>Then is it possible to convert it using <code>df.loc[:,'variant':'variant_param'].fillna(method='ffill',axis=1)['variant_param']</code>
  But from my code I only get like this</p>
  <pre><code>df =
         variant    variant_param    variant_new
    0        car    petro / young  petro / young
    1       bike     fred / trail    red / trail
    2     bottle              Nan         bottle
  </code></pre>
  <p>However, I need my dataframe into like this</p>
  <pre><code>df =
         variant    variant_param    variant_new
    0        car    petro / young          petro
    1        car    petro / young          young
    2       bike     fred / trail           fred
    3       bike     fred / trail          trail
    4     bottle              Nan         bottle
  </code></pre>