ENH: Styler.to_html gets bold_headers and caption kwarg (#43149)

Author: attack68

doc/source/whatsnew/v1.4.0.rst

@@ -73,7 +73,7 @@ Styler
   - Styling of indexing has been added, with :meth:`.Styler.apply_index` and :meth:`.Styler.applymap_index`. These mirror the signature of the methods already used to style data values, and work with both HTML and LaTeX format (:issue:`41893`).
   - :meth:`.Styler.bar` introduces additional arguments to control alignment and display (:issue:`26070`, :issue:`36419`), and it also validates the input arguments ``width`` and ``height`` (:issue:`42511`).
   - :meth:`.Styler.to_latex` introduces keyword argument ``environment``, which also allows a specific "longtable" entry through a separate jinja2 template (:issue:`41866`).
-  - :meth:`.Styler.to_html` introduces keyword arguments ``sparse_index`` and ``sparse_columns`` (:issue:`41946`)
+  - :meth:`.Styler.to_html` introduces keyword arguments ``sparse_index``, ``sparse_columns``, ``bold_headers``, ``caption`` (:issue:`41946`, :issue:`43149`).
   - Keyword argument ``level`` is added to :meth:`.Styler.hide_index` and :meth:`.Styler.hide_columns` for optionally controlling hidden levels in a MultiIndex (:issue:`25475`)
   - Global options have been extended to configure default ``Styler`` properties including formatting and encoding and mathjax options (:issue:`41395`)
 

pandas/io/formats/style.py

@@ -863,6 +863,8 @@ def to_html(
         table_attributes: str | None = None,
         sparse_index: bool | None = None,
         sparse_columns: bool | None = None,
+        bold_headers: bool = False,
+        caption: str | None = None,
         encoding: str | None = None,
         doctype_html: bool = False,
         exclude_styles: bool = False,
@@ -900,6 +902,14 @@ def to_html(
             will display each explicit level element in a hierarchical key for each
             column. Defaults to ``pandas.options.styler.sparse.columns`` value.
 
+            .. versionadded:: 1.4.0
+        bold_headers : bool, optional
+            Adds "font-weight: bold;" as a CSS property to table style header cells.
+
+            .. versionadded:: 1.4.0
+        caption : str, optional
+            Set, or overwrite, the caption on Styler before rendering.
+
             .. versionadded:: 1.4.0
         encoding : str, optional
             Character encoding setting for file output, and HTML meta tags.
@@ -938,6 +948,14 @@ def to_html(
         if sparse_columns is None:
             sparse_columns = get_option("styler.sparse.columns")
 
+        if bold_headers:
+            obj.set_table_styles(
+                [{"selector": "th", "props": "font-weight: bold;"}], overwrite=False
+            )
+
+        if caption is not None:
+            obj.set_caption(caption)
+
         encoding = encoding or get_option("styler.render.encoding")
         # Build HTML string..
         html = obj._render_html(

pandas/tests/io/formats/style/test_html.py

@@ -199,6 +199,20 @@ def test_doctype_encoding(styler):
         assert '<meta charset="ANSI">' in result
 
 
+def test_bold_headers_arg(styler):
+    result = styler.to_html(bold_headers=True)
+    assert "th {\n  font-weight: bold;\n}" in result
+    result = styler.to_html()
+    assert "th {\n  font-weight: bold;\n}" not in result
+
+
+def test_caption_arg(styler):
+    result = styler.to_html(caption="foo bar")
+    assert "<caption>foo bar</caption>" in result
+    result = styler.to_html()
+    assert "<caption>foo bar</caption>" not in result
+
+
 def test_block_names(tpl_style, tpl_table):
     # catch accidental removal of a block
     expected_style = {