add

Author: weikhor

pandas/core/groupby/generic.py

@@ -386,6 +386,9 @@ def _wrap_applied_output(
             )
         assert values is not None
 
+        if len(data) == 0 and len(values) != 0:
+            return values[0].to_frame().T.iloc[:0]
+
         if isinstance(values[0], dict):
             # GH #823 #24880
             index = self.grouper.result_index
@@ -1005,6 +1008,9 @@ def _wrap_applied_output(
             result = result.astype(data.dtypes, copy=False)
             return result
 
+        if len(data) == 0 and len(values) != 0:
+            return values[0].unstack().to_frame().T.iloc[:0]
+
         # GH12824
         first_not_none = next(com.not_none(*values), None)
 

pandas/core/groupby/groupby.py

@@ -2491,24 +2491,15 @@ def ohlc(self) -> DataFrame:
     @doc(DataFrame.describe)
     def describe(self, **kwargs):
         with self._group_selection_context():
-            if len(self._selected_obj) == 0:
-                if self._selected_obj.ndim == 1:
-                    return self._selected_obj.describe(**kwargs).to_frame().T.iloc[:0]
-                else:
-                    return (
-                        self._selected_obj.describe(**kwargs)
-                        .unstack()
-                        .to_frame()
-                        .T.iloc[:0]
-                    )
-
             result = self._python_apply_general(
                 lambda x: x.describe(**kwargs),
                 self._selected_obj,
                 not_indexed_same=True,
             )
             if self.axis == 1:
                 return result.T
+            elif len(result) == 0:
+                return result
             return result.unstack()
 
     @final

pandas/core/groupby/ops.py

@@ -792,7 +792,7 @@ def apply(
             # If group_keys is empty, then no function calls have been made,
             #  so we will not have raised even if this is an invalid dtype.
             #  So do one dummy call here to raise appropriate TypeError.
-            f(data.iloc[:0])
+            result_values.append(f(data.iloc[:0]))
 
         return result_values, mutated