Apply CSS class to Pandas DataFrame using to_html

Essentially, the pandas.to_html() just exports a plain HTML table. You can insert the table wherever you want in the body and control the style via CSS in the style section.

<html>
<head>
<style> 
  table, th, td {{font-size:10pt; border:1px solid black; border-collapse:collapse; text-align:left;}}
  th, td {{padding: 5px;}}
</style>
</head>
<body>
{
  pandas.to_html()
}
</body>
</html>

Pandas' to_html simply outputs a large string containing HTML table markup. The classes argument is a convenience handler to give the <table> a class attribute that will be referenced in a previously created CSS document that styles it. Therefore, incorporate to_html into a wider HTML document build that references an external CSS.

Interestingly, to_html adds dual classes <table class="dataframe mystyle"> which can be referenced in CSS individually, .dataframe {...} .mystyle{...}, or together .dataframe.mystyle {...}. Below demonstrates with random data.

Data

import pandas as pd
import numpy as np

pd.set_option('display.width', 1000)
pd.set_option('colheader_justify', 'center')

np.random.seed(6182018)
demo_df = pd.DataFrame({'date': np.random.choice(pd.date_range('2018-01-01', '2018-06-18', freq='D'), 50),
                        'analysis_tool': np.random.choice(['pandas', 'r', 'julia', 'sas', 'stata', 'spss'],50),              
                        'database': np.random.choice(['postgres', 'mysql', 'sqlite', 'oracle', 'sql server', 'db2'],50), 
                        'os': np.random.choice(['windows 10', 'ubuntu', 'mac os', 'android', 'ios', 'windows 7', 'debian'],50), 
                        'num1': np.random.randn(50)*100,
                        'num2': np.random.uniform(0,1,50),                   
                        'num3': np.random.randint(100, size=50),
                        'bool': np.random.choice([True, False], 50)
                       },
                        columns=['date', 'analysis_tool', 'num1', 'database', 'num2', 'os', 'num3', 'bool']
          )


print(demo_df.head(10))
#      date    analysis_tool     num1      database     num2        os      num3  bool 
# 0 2018-04-21     pandas     153.474246       mysql  0.658533         ios   74    True
# 1 2018-04-13        sas     199.461669      sqlite  0.656985   windows 7   11   False
# 2 2018-06-09      stata      12.918608      oracle  0.495707     android   25   False
# 3 2018-04-24       spss      88.562111  sql server  0.113580   windows 7   42   False
# 4 2018-05-05       spss     110.231277      oracle  0.660977  windows 10   76    True
# 5 2018-04-05        sas     -68.140295  sql server  0.346894  windows 10    0    True
# 6 2018-05-07      julia      12.874660    postgres  0.195217         ios   79    True
# 7 2018-01-22          r     189.410928       mysql  0.234815  windows 10   56   False
# 8 2018-01-12     pandas    -111.412564  sql server  0.580253      debian   30   False
# 9 2018-04-12          r      38.963967    postgres  0.266604   windows 7   46   False

CSS (save as df_style.css)

/* includes alternating gray and white with on-hover color */

.mystyle {
    font-size: 11pt; 
    font-family: Arial;
    border-collapse: collapse; 
    border: 1px solid silver;

}

.mystyle td, th {
    padding: 5px;
}

.mystyle tr:nth-child(even) {
    background: #E0E0E0;
}

.mystyle tr:hover {
    background: silver;
    cursor: pointer;
}

Pandas

pd.set_option('colheader_justify', 'center')   # FOR TABLE <th>

html_string = '''
<html>
  <head><title>HTML Pandas Dataframe with CSS</title></head>
  <link rel="stylesheet" type="text/css" href="df_style.css"/>
  <body>
    {table}
  </body>
</html>.
'''

# OUTPUT AN HTML FILE
with open('myhtml.html', 'w') as f:
    f.write(html_string.format(table=demo_df.to_html(classes='mystyle')))

OUTPUT

HTML (references df_style.css, assumed in same directory; see class argument in table)

<html>
  <head><title>HTML Pandas Dataframe with CSS</title></head>
  <link rel="stylesheet" type="text/css" href="df_style.css"/>
  <body>
    <table border="1" class="dataframe mystyle">
  <thead>
    <tr style="text-align: center;">
      <th></th>
      <th>date</th>
      <th>analysis_tool</th>
      <th>num1</th>
      <th>database</th>
      <th>num2</th>
      <th>os</th>
      <th>num3</th>
      <th>bool</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <th>0</th>
      <td>2018-04-21</td>
      <td>pandas</td>
      <td>153.474246</td>
      <td>mysql</td>
      <td>0.658533</td>
      <td>ios</td>
      <td>74</td>
      <td>True</td>
    </tr>
    <tr>
      <th>1</th>
      <td>2018-04-13</td>
      <td>sas</td>
      <td>199.461669</td>
      <td>sqlite</td>
      <td>0.656985</td>
      <td>windows 7</td>
      <td>11</td>
      <td>False</td>
    </tr>
    <tr>
      <th>2</th>
      <td>2018-06-09</td>
      <td>stata</td>
      <td>12.918608</td>
      <td>oracle</td>
      <td>0.495707</td>
      <td>android</td>
      <td>25</td>
      <td>False</td>
    </tr>
    <tr>
      <th>3</th>
      <td>2018-04-24</td>
      <td>spss</td>
      <td>88.562111</td>
      <td>sql server</td>
      <td>0.113580</td>
      <td>windows 7</td>
      <td>42</td>
      <td>False</td>
    </tr>
    <tr>
      <th>4</th>
      <td>2018-05-05</td>
      <td>spss</td>
      <td>110.231277</td>
      <td>oracle</td>
      <td>0.660977</td>
      <td>windows 10</td>
      <td>76</td>
      <td>True</td>
    </tr>
    ...
  </tbody>
</table>
  </body>
</html>

HTML Output