ENH: Styler.bar height control (pandas-dev#42483)

Author: attack68

doc/source/whatsnew/v1.4.0.rst

@@ -31,7 +31,7 @@ Other enhancements
 ^^^^^^^^^^^^^^^^^^
 - Add support for assigning values to ``by`` argument in :meth:`DataFrame.plot.hist` and :meth:`DataFrame.plot.box` (:issue:`15079`)
 - :meth:`Series.sample`, :meth:`DataFrame.sample`, and :meth:`.GroupBy.sample` now accept a ``np.random.Generator`` as input to ``random_state``. A generator will be more performant, especially with ``replace=False`` (:issue:`38100`)
--  Additional options added to :meth:`.Styler.bar` to control alignment and display (:issue:`26070`)
+-  Additional options added to :meth:`.Styler.bar` to control alignment and display, with keyword only arguments (:issue:`26070`, :issue:`36419`)
 - :meth:`Series.ewm`, :meth:`DataFrame.ewm`, now support a ``method`` argument with a ``'table'`` option that performs the windowing operation over an entire :class:`DataFrame`. See :ref:`Window Overview <window.overview>` for performance and functional benefits (:issue:`42273`)
 -
 

pandas/io/formats/style.py

@@ -2046,8 +2046,10 @@ def bar(
         self,
         subset: Subset | None = None,
         axis: Axis | None = 0,
+        *,
         color="#d65f5f",
         width: float = 100,
+        height: float = 100,
         align: str | float | int | Callable = "mid",
         vmin: float | None = None,
         vmax: float | None = None,
@@ -2056,6 +2058,8 @@ def bar(
         """
         Draw bar chart in the cell backgrounds.
 
+        .. versionchanged:: 1.4.0
+
         Parameters
         ----------
         subset : label, array-like, IndexSlice, optional
@@ -2074,6 +2078,10 @@ def bar(
         width : float, default 100
             The percentage of the cell, measured from the left, in which to draw the
             bars, in [0, 100].
+        height : float, default 100
+            The percentage height of the bar in the cell, centrally aligned, in [0,100].
+
+            .. versionadded:: 1.4.0
         align : str, int, float, callable, default 'mid'
             How to align the bars within the cells relative to a width adjusted center.
             If string must be one of:
@@ -2131,6 +2139,7 @@ def bar(
             align=align,
             colors=color,
             width=width / 100,
+            height=height / 100,
             vmin=vmin,
             vmax=vmax,
             base_css=props,
@@ -2791,6 +2800,7 @@ def _bar(
     align: str | float | int | Callable,
     colors: list[str],
     width: float,
+    height: float,
     vmin: float | None,
     vmax: float | None,
     base_css: str,
@@ -2808,6 +2818,9 @@ def _bar(
         Two listed colors as string in valid CSS.
     width : float in [0,1]
         The percentage of the cell, measured from left, where drawn bars will reside.
+    height : float in [0,1]
+        The percentage of the cell's height where drawn bars will reside, centrally
+        aligned.
     vmin : float, optional
         Overwrite the minimum value of the window.
     vmax : float, optional
@@ -2873,7 +2886,7 @@ def css_calc(x, left: float, right: float, align: str):
 
         Notes
         -----
-        Uses ``colors`` and ``width`` from outer scope.
+        Uses ``colors``, ``width`` and ``height`` from outer scope.
         """
         if pd.isna(x):
             return base_css
@@ -2911,7 +2924,13 @@ def css_calc(x, left: float, right: float, align: str):
             else:
                 start, end = z_frac, (x - left) / (right - left)
 
-        return css_bar(start * width, end * width, color)
+        ret = css_bar(start * width, end * width, color)
+        if height < 1 and "background: linear-gradient(" in ret:
+            return (
+                ret + f" no-repeat center; background-size: 100% {height * 100:.1f}%;"
+            )
+        else:
+            return ret
 
     values = data.to_numpy()
     left = np.nanmin(values) if vmin is None else vmin

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

@@ -275,6 +275,22 @@ def test_colors_mixed(align, exp):
     assert result == {(0, 0): exp[0], (1, 0): exp[1]}
 
 
+def test_bar_align_height():
+    # test when keyword height is used 'no-repeat center' and 'background-size' present
+    data = DataFrame([[1], [2]])
+    result = data.style.bar(align="left", height=50)._compute().ctx
+    bg_s = "linear-gradient(90deg, #d65f5f 100.0%, transparent 100.0%) no-repeat center"
+    expected = {
+        (0, 0): [("width", "10em")],
+        (1, 0): [
+            ("width", "10em"),
+            ("background", bg_s),
+            ("background-size", "100% 50.0%"),
+        ],
+    }
+    assert result == expected
+
+
 def test_bar_bad_align_raises():
     df = DataFrame({"A": [-100, -60, -30, -20]})
     msg = "`align` should be in {'left', 'right', 'mid', 'mean', 'zero'} or"