ENH: multicol naive implementation. part2 (#43382)

* multirow naive implementation
* amend tests for siunitx
* ivanovmg req
Co-authored-by: JHM Darbyshire (iMac) <[email protected]>

Author: attack68

pandas/core/config_init.py

@@ -896,7 +896,7 @@ def register_converter_cb(key):
         "latex.multicol_align",
         "r",
         styler_multicol_align,
-        validator=is_one_of_factory(["r", "c", "l"]),
+        validator=is_one_of_factory(["r", "c", "l", "naive-l", "naive-r"]),
     )
 
     cf.register_option(

pandas/io/formats/style.py

@@ -527,10 +527,13 @@ def to_latex(
             without multirow.
 
             .. versionchanged:: 1.4.0
-        multicol_align : {"r", "c", "l"}, optional
+        multicol_align : {"r", "c", "l", "naive-l", "naive-r"}, optional
             If sparsifying hierarchical MultiIndex columns whether to align text at
             the left, centrally, or at the right. If not given defaults to
-            ``pandas.options.styler.latex.multicol_align``
+            ``pandas.options.styler.latex.multicol_align``. If a naive option is
+            given renders without multicol.
+
+            .. versionchanged:: 1.4.0
         siunitx : bool, default False
             Set to ``True`` to structure LaTeX compatible with the {siunitx} package.
         environment : str, optional

pandas/io/formats/style_render.py

@@ -1410,6 +1410,14 @@ def _parse_latex_header_span(
         if 'colspan="' in attrs:
             colspan = attrs[attrs.find('colspan="') + 9 :]  # len('colspan="') = 9
             colspan = int(colspan[: colspan.find('"')])
+            if "naive-l" == multicol_align:
+                out = f"{{{display_val}}}" if wrap else f"{display_val}"
+                blanks = " & {}" if wrap else " &"
+                return out + blanks * (colspan - 1)
+            elif "naive-r" == multicol_align:
+                out = f"{{{display_val}}}" if wrap else f"{display_val}"
+                blanks = "{} & " if wrap else "& "
+                return blanks * (colspan - 1) + out
             return f"\\multicolumn{{{colspan}}}{{{multicol_align}}}{{{display_val}}}"
         elif 'rowspan="' in attrs:
             if multirow_align == "naive":

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

@@ -302,6 +302,35 @@ def test_multiindex_row_and_col(df_ext):
     assert result == expected
 
 
+@pytest.mark.parametrize(
+    "multicol_align, siunitx, header",
+    [
+        ("naive-l", False, " & A & &"),
+        ("naive-r", False, " & & & A"),
+        ("naive-l", True, "{} & {A} & {} & {}"),
+        ("naive-r", True, "{} & {} & {} & {A}"),
+    ],
+)
+def test_multicol_naive(df, multicol_align, siunitx, header):
+    ridx = MultiIndex.from_tuples([("A", "a"), ("A", "b"), ("A", "c")])
+    df.columns = ridx
+    level1 = " & a & b & c" if not siunitx else "{} & {a} & {b} & {c}"
+    col_format = "lrrl" if not siunitx else "lSSl"
+    expected = dedent(
+        f"""\
+        \\begin{{tabular}}{{{col_format}}}
+        {header} \\\\
+        {level1} \\\\
+        0 & 0 & -0.61 & ab \\\\
+        1 & 1 & -1.22 & cd \\\\
+        \\end{{tabular}}
+        """
+    )
+    styler = df.style.format(precision=2)
+    result = styler.to_latex(multicol_align=multicol_align, siunitx=siunitx)
+    assert expected == result
+
+
 def test_multi_options(df_ext):
     cidx = MultiIndex.from_tuples([("Z", "a"), ("Z", "b"), ("Y", "c")])
     ridx = MultiIndex.from_tuples([("A", "a"), ("A", "b"), ("B", "c")])