BUG: no apply to empty df in Styler (#45383)

Co-authored-by: JHM Darbyshire (iMac) <[email protected]>

Author: attack68

doc/source/whatsnew/v1.5.0.rst

@@ -20,6 +20,7 @@ Styler
 ^^^^^^
 
   - New method :meth:`.Styler.to_string` for alternative customisable output methods (:issue:`44502`)
+  - Various bug fixes, see below.
 
 .. _whatsnew_150.enhancements.enhancement2:
 
@@ -258,7 +259,7 @@ ExtensionArray
 
 Styler
 ^^^^^^
--
+- Minor bug when attempting to apply styling functions to an empty DataFrame subset (:issue:`45313`)
 -
 
 Other

pandas/io/formats/style.py

@@ -1486,7 +1486,9 @@ def _apply(
         subset = slice(None) if subset is None else subset
         subset = non_reducing_slice(subset)
         data = self.data.loc[subset]
-        if axis is None:
+        if data.empty:
+            result = DataFrame()
+        elif axis is None:
             result = func(data, **kwargs)
             if not isinstance(result, DataFrame):
                 if not isinstance(result, np.ndarray):

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

@@ -1548,3 +1548,9 @@ def test_col_trimming_hide_columns():
         assert ctx["head"][0][c + 2]["is_visible"] == vals[1]
 
     assert len(ctx["body"][0]) == 6  # index + 2 hidden + 2 visible + trimming col
+
+
+def test_no_empty_apply(mi_styler):
+    # 45313
+    mi_styler.apply(lambda s: ["a:v;"] * 2, subset=[False, False])
+    mi_styler._compute()