bugfix 26390 assigning pandas array to column works

Author: shantanu-gontia

pandas/core/frame.py

@@ -70,7 +70,7 @@
     is_sequence,
     is_named_tuple)
 from pandas.core.dtypes.generic import (
-    ABCSeries, ABCDataFrame, ABCIndexClass, ABCMultiIndex)
+    ABCSeries, ABCDataFrame, ABCIndexClass, ABCMultiIndex, ABCPandasArray)
 from pandas.core.dtypes.missing import isna, notna
 
 from pandas.core import algorithms
@@ -3620,6 +3620,11 @@ def reindexer(value):
             value = cast_scalar_to_array(len(self.index), value)
             value = maybe_cast_to_datetime(value, infer_dtype)
 
+        # convert pandas array to numpy array
+        if isinstance(value, ABCPandasArray):
+            value = value.to_numpy()
+            return np.atleast_2d(np.asarray(value))
+
         # return internal types directly
         if is_extension_type(value) or is_extension_array_dtype(value):
             return value

pandas/core/internals/blocks.py

@@ -3035,6 +3035,7 @@ def make_block(values, placement, klass=None, ndim=None, dtype=None,
     # For now, blocks should be backed by ndarrays when possible.
     if isinstance(values, ABCPandasArray):
         values = values.to_numpy()
+
     if isinstance(dtype, PandasDtype):
         dtype = dtype.numpy_dtype
 

pandas/tests/internals/test_internals.py

@@ -1310,3 +1310,12 @@ def test_make_block_no_pandas_array():
     result = make_block(arr.to_numpy(), slice(len(arr)), dtype=arr.dtype)
     assert result.is_integer is True
     assert result.is_extension is False
+
+
+def test_add_column_with_pandas_array():
+    # GH 26390
+    df = pd.DataFrame({'a': [1, 2, 3, 4], 'b': ['a', 'b', 'c', 'd']})
+    df['c'] = pd.array([1, 2, None, 3])
+    df2 = pd.DataFrame({'a': [1, 2, 3, 4], 'b': ['a', 'b', 'c', 'd'],
+                        'c': pd.array([1, 2, None, 3])})
+    assert_frame_equal(df, df2)