changes

Author: topper-123

pandas/core/arrays/base.py

@@ -456,6 +456,7 @@ def astype(self, dtype, copy=True):
         dtype = pandas_dtype(dtype)
         if isinstance(dtype, StringDtype):
             return dtype.construct_array_type()._from_sequence(self, copy=False)
+
         return np.array(self, dtype=dtype, copy=copy)
 
     def isna(self) -> ArrayLike:

pandas/core/arrays/period.py

@@ -564,6 +564,7 @@ def _format_native_types(self, na_rep="NaT", date_format=None, **kwargs):
         actually format my specific types
         """
         values = self.astype(object)
+
         if date_format:
             formatter = lambda dt: dt.strftime(date_format)
         else:

pandas/core/arrays/sparse/dtype.py

@@ -13,6 +13,7 @@
 from pandas.core.dtypes.cast import astype_nansafe
 from pandas.core.dtypes.common import (
     is_bool_dtype,
+    is_extension_array_dtype,
     is_object_dtype,
     is_scalar,
     is_string_dtype,
@@ -322,7 +323,10 @@ def update_dtype(self, dtype):
         dtype = pandas_dtype(dtype)
 
         if not isinstance(dtype, cls):
-            fill_value = astype_nansafe(np.array([self.fill_value]), dtype)[0]
+            if is_extension_array_dtype(dtype):
+                raise TypeError("sparse arrays of extension dtypes not supported")
+
+            fill_value = astype_nansafe(np.array(self.fill_value), dtype).item()
             dtype = cls(dtype, fill_value=fill_value)
 
         return dtype

pandas/tests/arrays/sparse/test_array.py

@@ -542,6 +542,7 @@ def test_astype_all(self, any_real_dtype):
                     np.array([0, 1], dtype="datetime64[ns]"),
                     dtype=SparseDtype("datetime64[ns]", pd.Timestamp("1970")),
                 ),
+                marks=[pytest.mark.xfail(reason="NumPy-7619")],
             ),
             (
                 SparseArray([0, 1, 10]),

pandas/tests/extension/test_numpy.py

@@ -141,6 +141,7 @@ def test_astype_str(self, data):
 
     @skip_nested
     def test_astype_string(self, data):
+        # GH-33465
         # ValueError: setting an array element with a sequence
         super().test_astype_string(data)
 

pandas/tests/extension/test_sparse.py

@@ -343,12 +343,13 @@ def test_astype_object_frame(self, all_data):
         # comp = result.dtypes.equals(df.dtypes)
         # assert not comp.any()
 
-    @pytest.mark.xfail(raises=AssertionError, reason="no sparse str dtype")
     def test_astype_str(self, data):
-        # Sparse arrays don't support str dtype
-        super().test_astype_str(data)
+        result = pd.Series(data[:5]).astype(str)
+        expected_dtype = pd.SparseDtype(str, str(data.fill_value))
+        expected = pd.Series([str(x) for x in data[:5]], dtype=expected_dtype)
+        self.assert_series_equal(result, expected)
 
-    @pytest.mark.xfail(raises=AssertionError, reason="no sparse StringDtype")
+    @pytest.mark.xfail(raises=TypeError, reason="no sparse StringDtype")
     def test_astype_string(self, data):
         super().test_astype_string(data)