DEPR: make arguments keyword only in to_dict

doc/source/whatsnew/v2.2.0.rst

@@ -93,6 +93,7 @@ Other API changes
 Deprecations
 ~~~~~~~~~~~~
 - Deprecated allowing non-keyword arguments in :meth:`DataFrame.to_csv` except ``path_or_buf``. (:issue:`54229`)
+- Deprecated allowing non-keyword arguments in :meth:`DataFrame.to_dict`. (:issue:`54229`)
 - Deprecated allowing non-keyword arguments in :meth:`DataFrame.to_hdf` except ``path_or_buf``. (:issue:`54229`)
 - Deprecated allowing non-keyword arguments in :meth:`DataFrame.to_html` except ``buf``. (:issue:`54229`)
 - Deprecated allowing non-keyword arguments in :meth:`DataFrame.to_json` except ``path_or_buf``. (:issue:`54229`)

pandas/core/frame.py

@@ -1933,6 +1933,9 @@ def to_dict(
     def to_dict(self, orient: Literal["records"], into: type[dict] = ...) -> list[dict]:
         ...
 
+    @deprecate_nonkeyword_arguments(
+        version="3.0", allowed_args=["self", "orient"], name="to_dict"
+    )
     def to_dict(
         self,
         orient: Literal[

pandas/tests/frame/methods/test_to_dict.py

@@ -99,27 +99,27 @@ def test_to_dict(self, mapping):
             for k2, v2 in v.items():
                 assert v2 == recons_data[k][k2]
 
-        recons_data = DataFrame(test_data).to_dict("list", mapping)
+        recons_data = DataFrame(test_data).to_dict("list", into=mapping)
 
         for k, v in test_data.items():
             for k2, v2 in v.items():
                 assert v2 == recons_data[k][int(k2) - 1]
 
-        recons_data = DataFrame(test_data).to_dict("series", mapping)
+        recons_data = DataFrame(test_data).to_dict("series", into=mapping)
 
         for k, v in test_data.items():
             for k2, v2 in v.items():
                 assert v2 == recons_data[k][k2]
 
-        recons_data = DataFrame(test_data).to_dict("split", mapping)
+        recons_data = DataFrame(test_data).to_dict("split", into=mapping)
         expected_split = {
             "columns": ["A", "B"],
             "index": ["1", "2", "3"],
             "data": [[1.0, "1"], [2.0, "2"], [np.nan, "3"]],
         }
         tm.assert_dict_equal(recons_data, expected_split)
 
-        recons_data = DataFrame(test_data).to_dict("records", mapping)
+        recons_data = DataFrame(test_data).to_dict("records", into=mapping)
         expected_records = [
             {"A": 1.0, "B": "1"},
             {"A": 2.0, "B": "2"},
@@ -494,3 +494,13 @@ def test_to_dict_masked_native_python(self):
         df = DataFrame({"a": Series([1, NA], dtype="Int64"), "B": 1})
         result = df.to_dict(orient="records")
         assert isinstance(result[0]["a"], int)
+
+    def test_to_dict_pos_args_deprecation(self):
+        # GH-54229
+        df = DataFrame({"a": [1, 2, 3]})
+        msg = (
+            r"Starting with pandas version 3.0 all arguments of to_dict except for the "
+            r"argument 'orient' will be keyword-only."
+        )
+        with tm.assert_produces_warning(FutureWarning, match=msg):
+            df.to_dict("records", {})