ENH: consistent Styler.highlight_X arg signature with props

doc/source/reference/style.rst

@@ -53,9 +53,9 @@ Builtin styles
 .. autosummary::
    :toctree: api/
 
+   Styler.highlight_null
    Styler.highlight_max
    Styler.highlight_min
-   Styler.highlight_null
    Styler.background_gradient
    Styler.bar
 

doc/source/whatsnew/v1.3.0.rst

@@ -135,6 +135,7 @@ Other enhancements
 - :meth:`.Styler.set_tooltips_class` and :meth:`.Styler.set_table_styles` amended to optionally allow certain css-string input arguments (:issue:`39564`)
 - :meth:`.Styler.apply` now more consistently accepts ndarray function returns, i.e. in all cases for ``axis`` is ``0, 1 or None`` (:issue:`39359`)
 - :meth:`.Styler.apply` and :meth:`.Styler.applymap` now raise errors if wrong format CSS is passed on render (:issue:`39660`)
+- Builtin highlighting methods in :class:`Styler` have a more consistent signature and css customisability (:issue:`40242`)
 - :meth:`Series.loc.__getitem__` and :meth:`Series.loc.__setitem__` with :class:`MultiIndex` now raising helpful error message when indexer has too many dimensions (:issue:`35349`)
 - :meth:`pandas.read_stata` and :class:`StataReader` support reading data from compressed files.
 - Add support for parsing ``ISO 8601``-like timestamps with negative signs to :meth:`pandas.Timedelta` (:issue:`37172`)

pandas/io/formats/style.py

@@ -941,7 +941,7 @@ def apply(
         Examples
         --------
         >>> def highlight_max(x, color):
-        ...     return np.where(x == np.nanmax(x.values), f"color: {color};", None)
+        ...     return np.where(x == np.nanmax(x.to_numpy()), f"color: {color};", None)
         >>> df = pd.DataFrame(np.random.randn(5, 2))
         >>> df.style.apply(highlight_max, color='red')
         >>> df.style.apply(highlight_max, color='blue', axis=1)
@@ -1636,9 +1636,10 @@ def highlight_null(
         self,
         null_color: str = "red",
         subset: Optional[IndexLabel] = None,
+        props: Optional[str] = None,
     ) -> Styler:
         """
-        Shade the background ``null_color`` for missing values.
+        Highlight missing values with a style.
 
         Parameters
         ----------
@@ -1648,79 +1649,114 @@ def highlight_null(
 
             .. versionadded:: 1.1.0
 
+        props : str, default None
+            CSS properties to use for highlighting. If ``props`` is given, ``color``
+            is not used.
+
+            .. versionadded:: 1.3.0
+
         Returns
         -------
         self : Styler
+
+        See Also
+        --------
+        Styler.highlight_max: Highlight the maximum with a style.
+        Styler.highlight_min: Highlight the minimum with a style.
         """
 
         def f(data: DataFrame, props: str) -> np.ndarray:
-            return np.where(pd.isna(data).values, props, "")
+            return np.where(pd.isna(data).to_numpy(), props, "")
 
-        return self.apply(
-            f, axis=None, subset=subset, props=f"background-color: {null_color};"
-        )
+        if props is None:
+            props = f"background-color: {null_color};"
+        return self.apply(f, axis=None, subset=subset, props=props)
 
     def highlight_max(
         self,
         subset: Optional[IndexLabel] = None,
         color: str = "yellow",
         axis: Optional[Axis] = 0,
+        props: Optional[str] = None,
     ) -> Styler:
         """
-        Highlight the maximum by shading the background.
+        Highlight the maximum with a style.
 
         Parameters
         ----------
         subset : IndexSlice, default None
             A valid slice for ``data`` to limit the style application to.
         color : str, default 'yellow'
+            Background color to use for highlighting.
         axis : {0 or 'index', 1 or 'columns', None}, default 0
             Apply to each column (``axis=0`` or ``'index'``), to each row
             (``axis=1`` or ``'columns'``), or to the entire DataFrame at once
             with ``axis=None``.
+        props : str, default None
+            CSS properties to use for highlighting. If ``props`` is given, ``color``
+            is not used.
+
+            .. versionadded:: 1.3.0
 
         Returns
         -------
         self : Styler
+
+        See Also
+        --------
+        Styler.highlight_null: Highlight missing values with a style.
+        Styler.highlight_min: Highlight the minimum with a style.
         """
 
         def f(data: FrameOrSeries, props: str) -> np.ndarray:
-            return np.where(data == np.nanmax(data.values), props, "")
+            return np.where(data == np.nanmax(data.to_numpy()), props, "")
 
-        return self.apply(
-            f, axis=axis, subset=subset, props=f"background-color: {color};"
-        )
+        if props is None:
+            props = f"background-color: {color};"
+        return self.apply(f, axis=axis, subset=subset, props=props)
 
     def highlight_min(
         self,
         subset: Optional[IndexLabel] = None,
         color: str = "yellow",
         axis: Optional[Axis] = 0,
+        props: Optional[str] = None,
     ) -> Styler:
         """
-        Highlight the minimum by shading the background.
+        Highlight the minimum with a style.
 
         Parameters
         ----------
         subset : IndexSlice, default None
             A valid slice for ``data`` to limit the style application to.
         color : str, default 'yellow'
+            Background color to use for highlighting.
         axis : {0 or 'index', 1 or 'columns', None}, default 0
             Apply to each column (``axis=0`` or ``'index'``), to each row
             (``axis=1`` or ``'columns'``), or to the entire DataFrame at once
             with ``axis=None``.
+        props : str, default None
+            CSS properties to use for highlighting. If ``props`` is given, ``color``
+            is not used.
+
+            .. versionadded:: 1.3.0
 
         Returns
         -------
         self : Styler
+
+        See Also
+        --------
+        Styler.highlight_null: Highlight missing values with a style.
+        Styler.highlight_max: Highlight the maximum with a style.
         """
 
         def f(data: FrameOrSeries, props: str) -> np.ndarray:
-            return np.where(data == np.nanmin(data.values), props, "")
+            return np.where(data == np.nanmin(data.to_numpy()), props, "")
 
-        return self.apply(
-            f, axis=axis, subset=subset, props=f"background-color: {color};"
-        )
+        if props is None:
+            props = f"background-color: {color};"
+        return self.apply(f, axis=axis, subset=subset, props=props)
 
     @classmethod
     def from_custom_template(cls, searchpath, name):

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

@@ -7,6 +7,11 @@
 
 
 class TestStylerHighlight:
+    def setup_method(self, method):
+        np.random.seed(24)
+        self.s = DataFrame({"A": np.random.permutation(range(6))})
+        self.df = DataFrame({"A": [0, 1], "B": np.random.randn(2)})
+
     def test_highlight_null(self):
         df = DataFrame({"A": [0, np.nan]})
         result = df.style.highlight_null()._compute().ctx
@@ -28,43 +33,33 @@ def test_highlight_null_subset(self):
         }
         assert result == expected
 
-    def test_highlight_max(self):
-        df = DataFrame([[1, 2], [3, 4]], columns=["A", "B"])
-        css_seq = [("background-color", "yellow")]
-        # max(df) = min(-df)
-        for max_ in [True, False]:
-            if max_:
-                attr = "highlight_max"
-            else:
-                df = -df
-                attr = "highlight_min"
-            result = getattr(df.style, attr)()._compute().ctx
-            assert result[(1, 1)] == css_seq
-
-            result = getattr(df.style, attr)(color="green")._compute().ctx
-            assert result[(1, 1)] == [("background-color", "green")]
-
-            result = getattr(df.style, attr)(subset="A")._compute().ctx
-            assert result[(1, 0)] == css_seq
-
-            result = getattr(df.style, attr)(axis=0)._compute().ctx
-            expected = {
-                (1, 0): css_seq,
-                (1, 1): css_seq,
-            }
-            assert result == expected
-
-            result = getattr(df.style, attr)(axis=1)._compute().ctx
-            expected = {
-                (0, 1): css_seq,
-                (1, 1): css_seq,
-            }
-            assert result == expected
-
-        # separate since we can't negate the strs
-        df["C"] = ["a", "b"]
-        result = df.style.highlight_max()._compute().ctx
-        expected = {(1, 1): css_seq}
+    @pytest.mark.parametrize("f", ["highlight_min", "highlight_max"])
+    def test_highlight_minmax_basic(self, f):
+        expected = {
+            (0, 0): [("background-color", "red")],
+            (1, 0): [("background-color", "red")],
+        }
+        if f == "highlight_min":
+            df = -self.df
+        else:
+            df = self.df
+        result = getattr(df.style, f)(axis=1, color="red")._compute().ctx
+        assert result == expected
 
-        result = df.style.highlight_min()._compute().ctx
-        expected = {(0, 0): css_seq}
+    @pytest.mark.parametrize("f", ["highlight_min", "highlight_max"])
+    @pytest.mark.parametrize(
+        "kwargs",
+        [
+            {"axis": None, "color": "red"},  # test axis
+            {"axis": 0, "subset": ["A"], "color": "red"},  # test subset
+            {"axis": None, "props": "background-color: red"},  # test props
+        ],
+    )
+    def test_highlight_minmax_ext(self, f, kwargs):
+        expected = {(1, 0): [("background-color", "red")]}
+        if f == "highlight_min":
+            df = -self.df
+        else:
+            df = self.df
+        result = getattr(df.style, f)(**kwargs)._compute().ctx
+        assert result == expected