title: Append column in a dataframe with string values
body: <p>I have a case where I am trying to append the calculated percent value in a understandable format into a column in my dataframe called df. When I say understandable format the output into the column should go like <code>'40% Matched'</code>, like in the case below.</p>
  
  <pre><code>df = pd.DataFrame({ 'Col1':[['Phone', 'Watch', 'Pen', 'Pencil', 'Knife'],['apple','orange','mango','cherry','banana','kiwi','tomato','avocado']], 'Col2': [['Phone', 'Watch', 'Pen', 'Pencil', 'fork'],['orange','avocado','kiwi','mango','grape','lemon','tomato']]})
  
  df['Matched Percent'] = 'No Match'
  
  for index,(lst1,lst2) in enumerate(zip(df['Col1'],df['Col2'])):
     if(lst1 == lst2):
        print('100% Matched')
     else:
        c1 = Counter(lst1)
        c2 = Counter(lst2)
        matching = {k: c1[k]+c2[k] for k in c1.keys() if k in c2}
        text = '% Matched'
        if len(lst1) &gt; len(lst2):
           out = round(len(matching)/len(lst1)*100)
           #df['Matched Percent'].append(out,'% Matched')
           print(out,'% Matched')
        else:
           out = round(len(matching)/len(lst2)*100)
           #df['Matched Percent'].append(out,'% Matched')
           print(out,'% Matched')
  
  80 % Matched
  62 % Matched
  
  TypeError: cannot concatenate object of type "&lt;class 'int'&gt;"; only pd.Series, pd.DataFrame, and pd.Panel (deprecated) objs are valid
  </code></pre>
  
  <p>I keep getting TypeError. I tried a couple of ways but no luck. I am able to print the values in the way I want in my screen as shown above. But when I append it to my dataframe <code>df</code> it fails. Appreciate advice on how to solve this.</p>