BUG: Ignore warning for duplicate columns in to_dict when orient='t…

…ight' (pandas-dev#58335)

* Ignore warning for duplicate columns in to_dict when orient='tight'

* Add whatsnew

* Update doc/source/whatsnew/v3.0.0.rst

Co-authored-by: Abdulaziz Aloqeely <52792999+Aloqeely@users.noreply.github.com>

* Update whatsnew and redefine duplicate columns

* Use assert instead

* assert not raise and equal

---------

Co-authored-by: Abdulaziz Aloqeely <52792999+Aloqeely@users.noreply.github.com>

pandas/core/methods/to_dict.py

@@ -148,7 +148,7 @@ def to_dict(
         Return a collections.abc.MutableMapping object representing the
         DataFrame. The resulting transformation depends on the `orient` parameter.
     """
-    if not df.columns.is_unique:
+    if orient != "tight" and not df.columns.is_unique:
         warnings.warn(
             "DataFrame columns are not unique, some columns will be omitted.",
             UserWarning,

pandas/tests/frame/methods/test_to_dict.py

@@ -513,6 +513,20 @@ def test_to_dict_masked_native_python(self):
         result = df.to_dict(orient="records")
         assert isinstance(result[0]["a"], int)
 
+    def test_to_dict_tight_no_warning_with_duplicate_column(self):
+        # GH#58281
+        df = DataFrame([[1, 2], [3, 4], [5, 6]], columns=["A", "A"])
+        with tm.assert_produces_warning(None):
+            result = df.to_dict(orient="tight")
+        expected = {
+            "index": [0, 1, 2],
+            "columns": ["A", "A"],
+            "data": [[1, 2], [3, 4], [5, 6]],
+            "index_names": [None],
+            "column_names": [None],
+        }
+        assert result == expected
+
 
 @pytest.mark.parametrize(
     "val", [Timestamp(2020, 1, 1), Timedelta(1), Period("2020"), Interval(1, 2)]