ENH: validate the argument width on Styler.bar

doc/source/whatsnew/v1.4.0.rst

@@ -32,6 +32,7 @@ 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`)
+- :meth:`Styler.bar` now validates the input argument ``width`` (:issue:`42511`)
 - :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

@@ -2121,6 +2121,9 @@ def bar(
                 "(eg: color=['#d65f5f', '#5fba7d'])"
             )
 
+        if not (0 <= width <= 100):
+            raise ValueError(f"`width` must be a value in [0, 100], got {width}")
+
         if subset is None:
             subset = self.data.select_dtypes(include=np.number).columns
 

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

@@ -319,8 +319,13 @@ def test_colors_mixed(align, exp):
     assert result == {(0, 0): exp[0], (1, 0): exp[1]}
 
 
-def test_bar_bad_align_raises():
+def test_bar_value_error_raises():
     df = DataFrame({"A": [-100, -60, -30, -20]})
+
     msg = "`align` should be in {'left', 'right', 'mid', 'mean', 'zero'} or"
     with pytest.raises(ValueError, match=msg):
-        df.style.bar(align="poorly", color=["#d65f5f", "#5fba7d"]).render()
+        df.style.bar(align="poorly", color=["#d65f5f", "#5fba7d"]).to_html()
+
+    msg = r"`width` must be a value in \[0, 100\]"
+    with pytest.raises(ValueError, match=msg):
+        df.style.bar(width=200).to_html()