title: Add a percent sign to a dataframe column in Python
body: <p>I've been attempting to add a percent sign to a column in my dataframe but to no avail. Would anyone have any idea?</p>
  
  <pre><code>import pandas as pd
  
  names = ('jimmy', 'red', 'julie', 'brad', 'oranges')
  score = (82, 38 , 55, 19, 33)
  
  df = pd.DataFrame({'Name': names, 'Grade': score})
  
  df
  Out[20]: 
     Grade     Name
  0     82    jimmy
  1     38      red
  2     55    julie
  3     19     brad
  4     33  oranges
  </code></pre>
  
  <p>I've made numerous attempts but nothing seems to work out. Here is one failed attempt:</p>
  
  <pre><code>df['Percent'] = str(df['Grade']) + '%'
  df['Percent']
  Out[22]: 
  0    0    82\n1    38\n2    55\n3    19\n4    33\nN...
  1    0    82\n1    38\n2    55\n3    19\n4    33\nN...
  2    0    82\n1    38\n2    55\n3    19\n4    33\nN...
  3    0    82\n1    38\n2    55\n3    19\n4    33\nN...
  4    0    82\n1    38\n2    55\n3    19\n4    33\nN...
  Name: Percent, dtype: object
  </code></pre>