test fix up

Author: attack68

pandas/core/generic.py

@@ -3227,6 +3227,7 @@ def to_latex(
     def to_latex(
         self,
         buf: FilePath | WriteBuffer[str] | None = None,
+        *,
         columns: Sequence[Hashable] | None = None,
         col_space: ColspaceArgType | None = None,
         header: bool_t | Sequence[str] = True,
@@ -3270,6 +3271,9 @@ def to_latex(
             The subset of columns to write. Writes all columns by default.
         col_space : int, optional
             The minimum width of each column.
+
+            .. deprecated:: 1.5.0
+               Whitespace does not affect a rendered LaTeX file and is ignored.
         header : bool or list of str, default True
             Write out the column names. If a list of strings is given,
             it is assumed to be aliases for the column names.
@@ -3366,6 +3370,13 @@ def to_latex(
         \bottomrule
         \end{{tabular}}
         """
+        msg = (
+            "`col_space` is deprecated. Whitespace in LaTeX does not impact "
+            "the rendered version, and this argument is ignored."
+        )
+        if col_space is not None:
+            warnings.warn(msg, DeprecationWarning, stacklevel=find_stack_level())
+
         # Get defaults from the pandas config
         if self.ndim == 1:
             self = self.to_frame()
@@ -3382,6 +3393,9 @@ def to_latex(
 
         if column_format is not None and not isinstance(column_format, str):
             raise ValueError("`column_format` must be str or unicode")
+        length = len(self.columns) if columns is None else len(columns)
+        if isinstance(header, (list, tuple)) and len(header) != length:
+            raise ValueError(f"Writing {length} cols but got {len(header)} aliases")
 
         # Refactor formatters/float_format/decimal/na_rep/escape to Styler structure
         base_format_ = {

pandas/tests/io/formats/test_to_latex.py

@@ -213,7 +213,7 @@ def test_to_latex_empty_longtable(self):
             \midrule
             \endhead
             \midrule
-            \multicolumn{1}{r}{Continued on next page} \\
+            \multicolumn{0}{r}{Continued on next page} \\
             \midrule
             \endfoot
             \bottomrule
@@ -377,7 +377,7 @@ def test_to_latex_number_of_items_in_header_missmatch_raises(
     ):
         # GH 7124
         df = DataFrame({"a": [1, 2], "b": ["b1", "b2"]})
-        msg = "``aliases`` must be of length equal to the number of visible labels"
+        msg = f"Writing 2 cols but got {num_aliases} aliases"
         with pytest.raises(ValueError, match=msg):
             df.to_latex(header=header)
 
@@ -1175,7 +1175,7 @@ def test_to_latex_index_has_name_tabular(self):
     def test_to_latex_groupby_tabular(self):
         # GH 10660
         df = DataFrame({"a": [0, 0, 1, 1], "b": list("abab"), "c": [1, 2, 3, 4]})
-        result = df.groupby("a").describe().to_latex(format={"precision": 1})
+        result = df.groupby("a").describe().to_latex(float_format="{:.1f}".format)
         expected = _dedent(
             r"""
             \begin{tabular}{lrrrrrrrr}