implemented additionally functionality of formatters_col in to_latex

doc/source/whatsnew/v1.2.0.rst

@@ -503,6 +503,9 @@ I/O
 - Bug in :class:`HDFStore` was dropping timezone information when exporting :class:`Series` with ``datetime64[ns, tz]`` dtypes with a fixed HDF5 store (:issue:`20594`)
 - :func:`read_csv` was closing user-provided binary file handles when ``engine="c"`` and an ``encoding`` was requested (:issue:`36980`)
 - Bug in :meth:`DataFrame.to_hdf` was not dropping missing rows with ``dropna=True`` (:issue:`35719`)
+- In :meth:`to_latex` ``formatters`` now handles ``fstring`` and ``callable`` paramaters (:issue:`26278`)
+
+
 
 Plotting
 ^^^^^^^^

pandas/core/generic.py

@@ -3034,10 +3034,14 @@ def to_latex(
             Write row names (index).
         na_rep : str, default 'NaN'
             Missing data representation.
-        formatters : list of functions or dict of {{str: function}}, optional
+        formatters : list of functions/str or dict of {{str: function}}, optional
             Formatter functions to apply to columns' elements by position or
             name. The result of each function must be a unicode string.
             List must be of length equal to the number of columns.
+
+            .. versionchanged:: 1.2
+               optionally allow fstrings in place of functions
+
         float_format : one-parameter function or str, optional, default None
             Formatter for floating point numbers. For example
             ``float_format="%.2f"`` and ``float_format="{{:0.2f}}".format`` will
@@ -3088,7 +3092,7 @@ def to_latex(
             .. versionadded:: 1.0.0
 
             .. versionchanged:: 1.2.0
-               Optionally allow caption to be a tuple ``(full_caption, short_caption)``.
+               optionally allow caption to be a tuple ``(full_caption, short_caption)``.
 
         label : str, optional
             The LaTeX label to be placed inside ``\label{{}}`` in the output.
@@ -3121,6 +3125,17 @@ def to_latex(
           Donatello &  purple &  bo staff \\
         \bottomrule
         \end{{tabular}}
+        >>> df = pd.DataFrame([[1,2], [3,4]], columns=['a','b'])
+        >>> print(df.to_latex(formatters=["d", ".3f"],
+        ...                   index=False)) # doctest: +NORMALIZE_WHITESPACE
+        \begin{{tabular}}{{rr}}
+          \toprule
+            a &     b \\
+          \midrule
+            1 & 2.000 \\
+            3 & 4.000 \\
+          \bottomrule
+        \end{{tabular}}
         """
         # Get defaults from the pandas config
         if self.ndim == 1:

pandas/io/formats/format.py

@@ -84,7 +84,11 @@
 
 
 FormattersType = Union[
-    List[Callable], Tuple[Callable, ...], Mapping[Union[str, int], Callable]
+    List[Callable],
+    Tuple[Callable, ...],
+    List[str],
+    List[Union[Callable, str]],
+    Mapping[Union[str, int], Callable],
 ]
 ColspaceType = Mapping[Label, Union[str, int]]
 ColspaceArgType = Union[
@@ -106,7 +110,7 @@
             Whether to print index (row) labels.
         na_rep : str, optional, default 'NaN'
             String representation of ``NaN`` to use.
-        formatters : list, tuple or dict of one-param. functions, optional
+        formatters : list, tuple or dict of one-param. functions, str, optional
             Formatter functions to apply to columns' elements by position or
             name.
             The result of each function must be a unicode string.
@@ -576,6 +580,24 @@ def _initialize_sparsify(self, sparsify: Optional[bool]) -> bool:
     def _initialize_formatters(
         self, formatters: Optional[FormattersType]
     ) -> FormattersType:
+        if is_list_like(formatters) and not isinstance(formatters, dict):
+            formatter_elems_type = all(
+                isinstance(elem, str) or callable(elem) for elem in formatters
+            )
+            if formatter_elems_type:
+                # two fold lambda is required to bypass lambda replication
+                # issues in list comprehensions
+                formatters = [
+                    (lambda style: lambda x: "{0:{1}}".format(x, style))(style)
+                    if isinstance(style, str)
+                    else style
+                    for style in formatters
+                ]
+            else:
+                raise ValueError(
+                    "Formatters elements should be f-strings or callable functions"
+                )
+
         if formatters is None:
             return {}
         elif len(self.frame.columns) == len(formatters) or isinstance(formatters, dict):

pandas/tests/io/formats/test_to_latex.py

@@ -121,6 +121,27 @@ def test_to_latex_column_format(self):
         )
         assert result == expected
 
+    def test_to_latex_with_float_format_list(self):
+        # GH: 26278
+        data = [[1, 2, 3], [4, 5, 6], [7, 8, 9.001]]
+        df = DataFrame(data, columns=["a", "b", "c"], index=["foo", "bar", "foobar"])
+
+        result = df.to_latex(formatters=["d", ".2f", lambda x: f"{x:.3f}"])
+        expected = _dedent(
+            r"""
+            \begin{tabular}{lrrr}
+            \toprule
+            {} & a &    b &     c \\
+            \midrule
+            foo    & 1 & 2.00 & 3.000 \\
+            bar    & 4 & 5.00 & 6.000 \\
+            foobar & 7 & 8.00 & 9.001 \\
+            \bottomrule
+            \end{tabular}
+            """
+        )
+        assert result == expected
+
     def test_to_latex_empty_tabular(self):
         df = DataFrame()
         result = df.to_latex()