Remove the special case for empty dataframes in to_html.

Fixes issue pandas-dev#6062.

Author: filmor

doc/source/release.rst

@@ -73,6 +73,7 @@ API Changes
 - ``dtypes`` and ``ftypes`` now return a series with ``dtype=object`` on empty containers (:issue:`5740`)
 - ``df.to_csv`` will now return a string of the CSV data if neither a target path nor a buffer is provided
   (:issue:`6061`)
+- ``df.to_html`` will now print out the header of an empty dataframe (:issue:`6062`)
 - The ``interpolate`` ``downcast`` keyword default has been changed from ``infer`` to
   ``None``. This is to preseve the original dtype unless explicitly requested otherwise (:issue:`6290`).
 - allow a Series to utilize index methods depending on its index type, e.g. ``Series.year`` is now defined

doc/source/v0.14.0.txt

@@ -41,6 +41,8 @@ These are out-of-bounds selections
 
 - The ``DataFrame.interpolate()`` ``downcast`` keyword default has been changed from ``infer`` to
   ``None``. This is to preseve the original dtype unless explicitly requested otherwise (:issue:`6290`).
+- When converting a dataframe to HTML it used to return `Empty DataFrame`. This special case has
+  been removed, instead a header with the column names is returned (:issue:`6062`).
 - allow a Series to utilize index methods depending on its index type, e.g. ``Series.year`` is now defined
   for a Series with a ``DatetimeIndex`` or a ``PeriodIndex``; trying this on a non-supported Index type will
   now raise a ``TypeError``. (:issue:`4551`, :issue:`4056`, :issue:`5519`)

pandas/core/format.py

@@ -694,17 +694,9 @@ def write_result(self, buf):
         self.write('<table border="1" class="%s">' % ' '.join(_classes),
                    indent)
 
-        if len(frame.columns) == 0 or len(frame.index) == 0:
-            self.write('<tbody>', indent + self.indent_delta)
-            self.write_tr([repr(frame.index),
-                           'Empty %s' % type(frame).__name__],
-                          indent + (2 * self.indent_delta),
-                          self.indent_delta)
-            self.write('</tbody>', indent + self.indent_delta)
-        else:
-            indent += self.indent_delta
-            indent = self._write_header(indent)
-            indent = self._write_body(indent)
+        indent += self.indent_delta
+        indent = self._write_header(indent)
+        indent = self._write_body(indent)
 
         self.write('</table>', indent)
         if self.fmt.show_dimensions:

pandas/tests/test_format.py

@@ -1588,11 +1588,12 @@ def test_to_html_with_classes(self):
         expected = dedent("""
 
             <table border="1" class="dataframe sortable draggable">
-              <tbody>
-                <tr>
-                  <td>Index([], dtype='object')</td>
-                  <td>Empty DataFrame</td>
+              <thead>
+                <tr style="text-align: right;">
+                  <th></th>
                 </tr>
+              </thead>
+              <tbody>
               </tbody>
             </table>