pandas to_html no value representation

dataframe, pandas, python

Solution

It looks like the `float_format` doesn't play nice with `na_rep`. However, you can work around it if you pass a function to `float_format` that conditionally handles your NaNs along with the float formatting you want:

>>> df

  Group    Data
0     A  1.2225
1     A     NaN

Reproducing your problem:

>>> out = StringIO()
>>> df.to_html(out,na_rep="Ted",float_format='{0:.2f}'.format)
>>> out.getvalue()

<table border="1" class="dataframe">
  <thead>
    <tr style="text-align: right;">
      <th></th>
      <th>Group</th>
      <th>Data</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <th>0</th>
      <td> A</td>
      <td>1.22</td>
    </tr>
    <tr>
      <th>1</th>
      <td> A</td>
      <td> nan</td>
    </tr>
  </tbody>

So you get the proper float precision but not the correct `na_rep`. But the following seems to work:

>>> out = StringIO()
>>> fmt = lambda x: '{0:.2f}'.format(x) if pd.notnull(x) else 'Ted'
>>> df.to_html(out,float_format=fmt)
>>> out.getvalue()

<table border="1" class="dataframe">
  <thead>
    <tr style="text-align: right;">
      <th></th>
      <th>Group</th>
      <th>Data</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <th>0</th>
      <td> A</td>
      <td>1.22</td>
    </tr>
    <tr>
      <th>1</th>
      <td> A</td>
      <td> Ted</td>
    </tr>
  </tbody>
</table>

Problem

When I run the line below, the NaN number in the dataframe does not get modified. Utilizing the exact same argument with `.to_csv()`, I get the expected result. Does `.to_html` require something different? `df.to_html('file.html', float_format='{0:.2f}'.format, na_rep="NA_REP")`

Original source