BUG: Interpolate not respecting inplace for empty df (pandas-dev#53223)

Author: phofl

doc/source/whatsnew/v2.1.0.rst

@@ -371,6 +371,7 @@ Indexing
 
 Missing
 ^^^^^^^
+- Bug in :meth:`DataFrame.interpolate` ignoring ``inplace`` when :class:`DataFrame` is empty (:issue:`53199`)
 - Bug in :meth:`Series.interpolate` and :meth:`DataFrame.interpolate` failing to raise on invalid ``downcast`` keyword, which can be only ``None`` or "infer" (:issue:`53103`)
 -
 

pandas/core/generic.py

@@ -7778,6 +7778,8 @@ def interpolate(
         obj = self.T if should_transpose else self
 
         if obj.empty:
+            if inplace:
+                return None
             return self.copy()
 
         if method not in fillna_methods:

pandas/tests/frame/methods/test_interpolate.py

@@ -437,3 +437,11 @@ def test_interp_fillna_methods(self, request, axis, method, using_array_manager)
         expected = df.fillna(axis=axis, method=method)
         result = df.interpolate(method=method, axis=axis)
         tm.assert_frame_equal(result, expected)
+
+    def test_interpolate_empty_df(self):
+        # GH#53199
+        df = DataFrame()
+        expected = df.copy()
+        result = df.interpolate(inplace=True)
+        assert result is None
+        tm.assert_frame_equal(df, expected)