BUG&TST: HTML formatting error in Styler.render() in rowspan attribute

doc/source/whatsnew/v1.2.0.rst

@@ -766,6 +766,10 @@ Plotting
 - Bug in :meth:`DataFrame.plot` and :meth:`Series.plot` was overwriting matplotlib's shared y axes behaviour when no ``sharey`` parameter was passed (:issue:`37942`)
 - Bug in :meth:`DataFrame.plot` was raising a ``TypeError`` with ``ExtensionDtype`` columns (:issue:`32073`)
 
+Styler
+^^^^^^
+
+- Bug in :meth:`Styler.render` HTML was generated incorrectly beacause of formatting error in rowspan attribute, it now matches with w3 syntax. (:issue:`38234`)
 
 Groupby/resample/rolling
 ^^^^^^^^^^^^^^^^^^^^^^^^

pandas/io/formats/style.py

@@ -389,7 +389,7 @@ def format_attr(pair):
  rowspan = idx_lengths.get((c, r), 0)
  if rowspan > 1:
  es["attributes"] = [
- format_attr({"key": "rowspan", "value": rowspan})
+ format_attr({"key": "rowspan", "value": f'"{rowspan}"'})
  ]
  row_es.append(es)
 

pandas/tests/io/formats/test_style.py

@@ -1411,7 +1411,7 @@ def test_mi_sparse(self):
  "display_value": "a",
  "is_visible": True,
  "type": "th",
- "attributes": ["rowspan=2"],
+ "attributes": ['rowspan="2"'],
  "class": "row_heading level0 row0",
  "id": "level0_row0",
  }
@@ -1740,6 +1740,15 @@ def test_colspan_w3(self):
  s = Styler(df, uuid="_", cell_ids=False)
  assert '<th class="col_heading level0 col0" colspan="2">l0</th>' in s.render()
 
+ def test_rowspan_w3(self):
+ # GH 38533
+ df = DataFrame(data=[[1, 2]], index=[["l0", "l0"], ["l1a", "l1b"]])
+ s = Styler(df, uuid="_", cell_ids=False)
+ assert (
+ '<th id="T___level0_row0" class="row_heading '
+ 'level0 row0" rowspan="2">l0</th>' in s.render()
+ )
+
  @pytest.mark.parametrize("len_", [1, 5, 32, 33, 100])
  def test_uuid_len(self, len_):
  # GH 36345