ENH: Add support for DataFrame(Categorical) (#11363) (#30305)

Author: proost

doc/source/whatsnew/v1.0.0.rst

@@ -206,6 +206,7 @@ Other enhancements
   now preserve those data types with pyarrow >= 1.0.0 (:issue:`20612`).
 - The ``partition_cols`` argument in :meth:`DataFrame.to_parquet` now accepts a string (:issue:`27117`)
 - :func:`to_parquet` now appropriately handles the ``schema`` argument for user defined schemas in the pyarrow engine. (:issue: `30270`)
+- DataFrame constructor preserve `ExtensionArray` dtype with `ExtensionArray` (:issue:`11363`)
 
 
 Build Changes

pandas/core/frame.py

@@ -450,7 +450,7 @@ def __init__(
 
         # For data is list-like, or Iterable (will consume into list)
         elif isinstance(data, abc.Iterable) and not isinstance(data, (str, bytes)):
-            if not isinstance(data, abc.Sequence):
+            if not isinstance(data, (abc.Sequence, ExtensionArray)):
                 data = list(data)
             if len(data) > 0:
                 if is_list_like(data[0]) and getattr(data[0], "ndim", 1) == 1:

pandas/tests/frame/test_constructors.py

@@ -25,6 +25,7 @@
     date_range,
     isna,
 )
+from pandas.arrays import IntervalArray, PeriodArray
 from pandas.core.construction import create_series_with_explicit_dtype
 import pandas.util.testing as tm
 
@@ -2396,6 +2397,21 @@ class List(list):
         result = DataFrame(List([List([1, 2, 3]), List([4, 5, 6])]))
         tm.assert_frame_equal(result, expected)
 
+    @pytest.mark.parametrize(
+        "extension_arr",
+        [
+            Categorical(list("aabbc")),
+            pd.SparseArray([1, np.nan, np.nan, np.nan]),
+            IntervalArray([pd.Interval(0, 1), pd.Interval(1, 5)]),
+            PeriodArray(pd.period_range(start="1/1/2017", end="1/1/2018", freq="M")),
+        ],
+    )
+    def test_constructor_with_extension_array(self, extension_arr):
+        # GH11363
+        expected = DataFrame(Series(extension_arr))
+        result = DataFrame(extension_arr)
+        tm.assert_frame_equal(result, expected)
+
 
 class TestDataFrameConstructorWithDatetimeTZ:
     def test_from_dict(self):