ENH: to_excel engine_kwargs for header autofilter and header bold (xlsxwriter/openpyxl); tests. Closes #62651

Author: antznette1

pandas/io/excel/_openpyxl.py

@@ -67,6 +67,9 @@ def __init__(  # pyright: ignore[reportInconsistentConstructor]
             engine_kwargs=engine_kwargs,
         )
 
+        # Persist engine kwargs for later feature toggles (e.g., autofilter/header bold)
+        self._engine_kwargs = engine_kwargs
+
         # ExcelWriter replaced "a" by "r+" to allow us to first read the excel file from
         # the file and later write to it
         if "r+" in self._mode:  # Load from existing workbook
@@ -486,6 +489,15 @@ def _write_cells(
                 row=freeze_panes[0] + 1, column=freeze_panes[1] + 1
             )
 
+        # Track bounds for autofilter application
+        min_row = None
+        min_col = None
+        max_row = None
+        max_col = None
+
+        # Prepare header bold setting
+        header_bold = bool(self._engine_kwargs.get("header_bold", False)) if hasattr(self, "_engine_kwargs") else False
+
         for cell in cells:
             xcell = wks.cell(
                 row=startrow + cell.row + 1, column=startcol + cell.col + 1
@@ -506,6 +518,26 @@ def _write_cells(
                 for k, v in style_kwargs.items():
                     setattr(xcell, k, v)
 
+            # Update bounds
+            crow = startrow + cell.row + 1
+            ccol = startcol + cell.col + 1
+            if min_row is None or crow < min_row:
+                min_row = crow
+            if min_col is None or ccol < min_col:
+                min_col = ccol
+            if max_row is None or crow > max_row:
+                max_row = crow
+            if max_col is None or ccol > max_col:
+                max_col = ccol
+
+            # Apply bold to first header row cells if requested
+            if header_bold and (cell.row == 0):
+                try:
+                    from openpyxl.styles import Font
+                    xcell.font = Font(bold=True)
+                except Exception:
+                    pass
+
             if cell.mergestart is not None and cell.mergeend is not None:
                 wks.merge_cells(
                     start_row=startrow + cell.row + 1,
@@ -532,6 +564,17 @@ def _write_cells(
                             for k, v in style_kwargs.items():
                                 setattr(xcell, k, v)
 
+        # Apply autofilter over the used range if requested
+        if hasattr(self, "_engine_kwargs") and bool(self._engine_kwargs.get("autofilter_header", False)):
+            if min_row is not None and min_col is not None and max_row is not None and max_col is not None:
+                try:
+                    from openpyxl.utils import get_column_letter
+                    start_ref = f"{get_column_letter(min_col)}{min_row}"
+                    end_ref = f"{get_column_letter(max_col)}{max_row}"
+                    wks.auto_filter.ref = f"{start_ref}:{end_ref}"
+                except Exception:
+                    pass
+
 
 class OpenpyxlReader(BaseExcelReader["Workbook"]):
     @doc(storage_options=_shared_docs["storage_options"])

pandas/io/excel/_xlsxwriter.py

@@ -212,6 +212,8 @@ def __init__(  # pyright: ignore[reportInconsistentConstructor]
             engine_kwargs=engine_kwargs,
         )
 
+        self._engine_kwargs = engine_kwargs
+
         try:
             self._book = Workbook(self._handles.handle, **engine_kwargs)  # type: ignore[arg-type]
         except TypeError:
@@ -258,6 +260,14 @@ def _write_cells(
         if validate_freeze_panes(freeze_panes):
             wks.freeze_panes(*(freeze_panes))
 
+        min_row = None
+        min_col = None
+        max_row = None
+        max_col = None
+
+        header_bold = bool(self._engine_kwargs.get("header_bold", False)) if hasattr(self, "_engine_kwargs") else False
+        bold_format = self.book.add_format({"bold": True}) if header_bold else None
+
         for cell in cells:
             val, fmt = self._value_with_fmt(cell.val)
 
@@ -271,14 +281,35 @@ def _write_cells(
                 style = self.book.add_format(_XlsxStyler.convert(cell.style, fmt))
                 style_dict[stylekey] = style
 
+            crow = startrow + cell.row
+            ccol = startcol + cell.col
+            if min_row is None or crow < min_row:
+                min_row = crow
+            if min_col is None or ccol < min_col:
+                min_col = ccol
+            if max_row is None or crow > max_row:
+                max_row = crow
+            if max_col is None or ccol > max_col:
+                max_col = ccol
+
             if cell.mergestart is not None and cell.mergeend is not None:
                 wks.merge_range(
-                    startrow + cell.row,
-                    startcol + cell.col,
+                    crow,
+                    ccol,
                     startrow + cell.mergestart,
                     startcol + cell.mergeend,
                     val,
                     style,
                 )
             else:
-                wks.write(startrow + cell.row, startcol + cell.col, val, style)
+                if bold_format is not None and (startrow == crow):
+                    wks.write(crow, ccol, val, bold_format)
+                else:
+                    wks.write(crow, ccol, val, style)
+
+        if hasattr(self, "_engine_kwargs") and bool(self._engine_kwargs.get("autofilter_header", False)):
+            if min_row is not None and min_col is not None and max_row is not None and max_col is not None:
+                try:
+                    wks.autofilter(min_row, min_col, max_row, max_col)
+                except Exception:
+                    pass

pandas/io/formats/excel.py

@@ -922,6 +922,15 @@ def write(
         formatted_cells = self.get_formatted_cells()
         if isinstance(writer, ExcelWriter):
             need_save = False
+            # Propagate engine_kwargs to an existing writer instance if provided
+            if engine_kwargs:
+                try:
+                    current = getattr(writer, "_engine_kwargs", {}) or {}
+                    merged = {**current, **engine_kwargs}
+                    setattr(writer, "_engine_kwargs", merged)
+                except Exception:
+                    # Best-effort propagation; ignore if engine does not support it
+                    pass
         else:
             writer = ExcelWriter(
                 writer,

pandas/tests/io/excel/test_autofilter_openpyxl.py

@@ -0,0 +1,24 @@
+import io
+import pytest
+import pandas as pd
+
+openpyxl = pytest.importorskip("openpyxl")
+
+
+def test_to_excel_openpyxl_autofilter_and_bold():
+    df = pd.DataFrame({"A": [1, 2], "B": [3, 4]})
+    buf = io.BytesIO()
+    with pd.ExcelWriter(buf, engine="openpyxl") as writer:
+        df.to_excel(
+            writer,
+            index=False,
+            engine_kwargs={"autofilter_header": True, "header_bold": True},
+        )
+    buf.seek(0)
+    wb = openpyxl.load_workbook(buf)
+    ws = wb.active
+    # Autofilter should be set spanning header+data
+    assert ws.auto_filter is not None
+    assert ws.auto_filter.ref is not None and ws.auto_filter.ref != ""
+    # Header row (row 1) should be bold
+    assert all(ws.cell(row=1, column=c).font.bold for c in range(1, df.shape[1] + 1))

pandas/tests/io/excel/test_autofilter_xlsxwriter.py

@@ -0,0 +1,25 @@
+import io
+import pytest
+import pandas as pd
+
+pytest.importorskip("xlsxwriter")
+openpyxl = pytest.importorskip("openpyxl")
+
+
+def test_to_excel_xlsxwriter_autofilter_and_bold():
+    df = pd.DataFrame({"A": [1, 2], "B": [3, 4]})
+    buf = io.BytesIO()
+    with pd.ExcelWriter(buf, engine="xlsxwriter") as writer:
+        df.to_excel(
+            writer,
+            index=False,
+            engine_kwargs={"autofilter_header": True, "header_bold": True},
+        )
+    buf.seek(0)
+    wb = openpyxl.load_workbook(buf)
+    ws = wb.active
+    # Autofilter should be set spanning header+data
+    assert ws.auto_filter is not None
+    assert ws.auto_filter.ref is not None and ws.auto_filter.ref != ""
+    # Header row (row 1) should be bold
+    assert all(ws.cell(row=1, column=c).font.bold for c in range(1, df.shape[1] + 1))