ENH: exclude html table border w/falsy value

Per the HTML5 spec, border attributes on table elements are obsolete.
Borders should be implemented via CSS instead.
https://html.spec.whatwg.org/multipage/obsolete.html#attr-table-border
This enhancement will retain the default behavior of the border keyword of to_html,
but will exclude the attribute entirely upon receiving a falsy value.

doc/source/whatsnew/v1.5.0.rst

@@ -39,8 +39,7 @@ Other enhancements
 - :meth:`.GroupBy.min` and :meth:`.GroupBy.max` now supports `Numba <https://numba.pydata.org/>`_ execution with the ``engine`` keyword (:issue:`45428`)
 - Implemented a ``bool``-dtype :class:`Index`, passing a bool-dtype array-like to ``pd.Index`` will now retain ``bool`` dtype instead of casting to ``object`` (:issue:`45061`)
 - Implemented a complex-dtype :class:`Index`, passing a complex-dtype array-like to ``pd.Index`` will now retain complex dtype instead of casting to ``object`` (:issue:`45845`)
-
--
+- :meth:`to_html` now excludes the ``border`` attribute from ``<table>`` elements when a falsy value is passed to the ``border`` keyword.
 
 .. ---------------------------------------------------------------------------
 .. _whatsnew_150.notable_bug_fixes:

pandas/core/frame.py

@@ -2883,7 +2883,7 @@ def to_html(
         classes: str | list | tuple | None = None,
         escape: bool = True,
         notebook: bool = False,
-        border: int | None = None,
+        border: int | bool | None = None,
         table_id: str | None = None,
         render_links: bool = False,
         encoding: str | None = None,

pandas/io/formats/format.py

@@ -1058,7 +1058,7 @@ def to_html(
         encoding: str | None = None,
         classes: str | list | tuple | None = None,
         notebook: bool = False,
-        border: int | None = None,
+        border: int | bool | None = None,
         table_id: str | None = None,
         render_links: bool = False,
     ) -> str | None:

pandas/io/formats/html.py

@@ -44,7 +44,7 @@ def __init__(
         self,
         formatter: DataFrameFormatter,
         classes: str | list[str] | tuple[str, ...] | None = None,
-        border: int | None = None,
+        border: int | bool | None = None,
         table_id: str | None = None,
         render_links: bool = False,
     ) -> None:
@@ -61,6 +61,9 @@ def __init__(
             border = cast(int, get_option("display.html.border"))
         elif not border:
             border = None
+        elif isinstance(border, bool):  # border=True
+            border = cast(int, get_option("display.html.border"))
+
         self.border = border
         self.table_id = table_id
         self.render_links = render_links

pandas/tests/io/test_html.py

@@ -1132,6 +1132,23 @@ def test_to_html_timestamp(self):
         result = df.to_html()
         assert "2000-01-01" in result
 
+    def test_to_html_borderless(self):
+        df = DataFrame([{'A': 1, 'B': 2}])
+        out_border_default = df.to_html()
+        out_border_true = df.to_html(border=True)
+        out_border_explicit_default = df.to_html(border=1)
+        out_border_nondefault = df.to_html(border=2)
+        out_border_false = df.to_html(border=False)
+        out_border_zero = df.to_html(border=0)
+
+        assert ' border="1"' in out_border_default
+        assert out_border_true == out_border_default
+        assert out_border_default == out_border_explicit_default
+        assert out_border_default != out_border_nondefault
+        assert ' border="2"' in out_border_nondefault
+        assert " border" not in out_border_false
+        assert out_border_zero == out_border_false
+
     @pytest.mark.parametrize(
         "displayed_only,exp0,exp1",
         [