Merge #204

204: fix astype r=andrewgsavage a=andrewgsavage

- [x] Closes #203 
- [ ] Executed `pre-commit run --all-files` with no errors
- [ ] The change is fully covered by automated unit tests
- [ ] Documented in docs/ as appropriate
- [ ] Added an entry to the CHANGES file


Co-authored-by: Andrew <andrewgsavage@gmail.com>

CHANGES

@@ -4,7 +4,7 @@ pint-pandas Changelog
 0.6 (unreleased)
 ----------------
 
-- Nothing changed yet.
+- Fix astype issue #196
 
 
 0.5 (2023-09-07)

pint_pandas/pint_array.py

@@ -417,7 +417,9 @@ def astype(self, dtype, copy=True):
             return self._to_array_of_quantity(copy=copy)
         if is_string_dtype(dtype):
             return pd.array([str(x) for x in self.quantity], dtype=dtype)
-        return pd.array(self.quantity, dtype, copy)
+        if isinstance(self._data, ExtensionArray):
+            return self._data.astype(dtype, copy=copy)
+        return pd.array(self.quantity.m, dtype, copy)
 
     @property
     def units(self):

pint_pandas/testsuite/test_issues.py

@@ -185,3 +185,12 @@ def test_sum(self):
         expected_2 = pd.Series([3, 12], dtype="pint[m]")
 
         tm.assert_series_equal(col_sum, expected_2)
+
+
+@pytest.mark.parametrize("dtype", [pd.Float64Dtype(), "float"])
+def test_issue_194(dtype):
+    s0 = pd.Series([1.0, 2.5], dtype=dtype)
+    s1 = s0.astype("pint[dimensionless]")
+    s2 = s1.astype(dtype)
+
+    tm.assert_series_equal(s0, s2)