PERF: BooleanArray._from_sequence_of_strings (#50613)

Author: lukemanley

doc/source/whatsnew/v2.0.0.rst

@@ -779,6 +779,7 @@ Performance improvements
 - Performance improvement in :meth:`~arrays.ArrowExtensionArray.__setitem__` when key is a null slice (:issue:`50248`)
 - Performance improvement in :class:`~arrays.ArrowExtensionArray` comparison methods when array contains NA (:issue:`50524`)
 - Performance improvement in :meth:`~arrays.ArrowExtensionArray.to_numpy` (:issue:`49973`)
+- Performance improvement when parsing strings to :class:`BooleanDtype` (:issue:`50613`)
 - Performance improvement in :meth:`DataFrame.join` when joining on a subset of a :class:`MultiIndex` (:issue:`48611`)
 - Performance improvement for :meth:`MultiIndex.intersection` (:issue:`48604`)
 - Performance improvement in ``var`` and ``std`` for nullable dtypes (:issue:`48379`).

pandas/core/arrays/boolean.py

@@ -321,17 +321,17 @@ def _from_sequence_of_strings(
         true_values_union = cls._TRUE_VALUES.union(true_values or [])
         false_values_union = cls._FALSE_VALUES.union(false_values or [])
 
-        def map_string(s):
-            if isna(s):
-                return s
-            elif s in true_values_union:
+        def map_string(s) -> bool:
+            if s in true_values_union:
                 return True
             elif s in false_values_union:
                 return False
             else:
                 raise ValueError(f"{s} cannot be cast to bool")
 
-        scalars = [map_string(x) for x in strings]
+        scalars = np.array(strings, dtype=object)
+        mask = isna(scalars)
+        scalars[~mask] = list(map(map_string, scalars[~mask]))
         return cls._from_sequence(scalars, dtype=dtype, copy=copy)
 
     _HANDLED_TYPES = (np.ndarray, numbers.Number, bool, np.bool_)

pandas/tests/extension/test_arrow.py

@@ -294,12 +294,6 @@ def test_from_sequence_of_strings_pa_array(self, data, request):
                     reason=f"pyarrow doesn't support parsing {pa_dtype}",
                 )
             )
-        elif pa.types.is_boolean(pa_dtype):
-            request.node.add_marker(
-                pytest.mark.xfail(
-                    reason="Iterating over ChunkedArray[bool] returns PyArrow scalars.",
-                )
-            )
         elif pa.types.is_timestamp(pa_dtype) and pa_dtype.tz is not None:
             if pa_version_under7p0:
                 request.node.add_marker(