return early if set_levels is empty

quangngd · quangngd · commit 7fb30fc89e4b · 2025-02-02T15:53:24.000+07:00
diff --git a/pandas/core/reshape/reshape.py b/pandas/core/reshape/reshape.py
@@ -930,6 +930,8 @@ def stack_v3(frame: DataFrame, level: list[int]) -> Series | DataFrame:
     if frame.columns.nunique() != len(frame.columns):
         raise ValueError("Columns with duplicate values are not supported in stack")
     set_levels = set(level)
+    if not len(set_levels):
+        return frame
     stack_cols = frame.columns._drop_level_numbers(
         [k for k in range(frame.columns.nlevels - 1, -1, -1) if k not in set_levels]
     )

Original file line number	Diff line number	Diff line change
`@@ -930,6 +930,8 @@ def stack_v3(frame: DataFrame, level: list[int]) -> Series \| DataFrame:`
`930`	`930`	`if frame.columns.nunique() != len(frame.columns):`
`931`	`931`	`raise ValueError("Columns with duplicate values are not supported in stack")`
`932`	`932`	`set_levels = set(level)`
	`933`	`+ if not len(set_levels):`
	`934`	`+ return frame`
`933`	`935`	`stack_cols = frame.columns._drop_level_numbers(`
`934`	`936`	`[k for k in range(frame.columns.nlevels - 1, -1, -1) if k not in set_levels]`
`935`	`937`	`)`