Call finalize in Series.str (#37015)

Author: TomAugspurger

doc/source/whatsnew/v1.2.0.rst

@@ -475,7 +475,7 @@ Other
 
 - Bug in :meth:`DataFrame.replace` and :meth:`Series.replace` incorrectly raising ``AssertionError`` instead of ``ValueError`` when invalid parameter combinations are passed (:issue:`36045`)
 - Bug in :meth:`DataFrame.replace` and :meth:`Series.replace` with numeric values and string ``to_replace`` (:issue:`34789`)
-- Fixed metadata propagation in the :class:`Series.dt` accessor (:issue:`28283`)
+- Fixed metadata propagation in the :class:`Series.dt` and :class:`Series.str` accessors (:issue:`28283`)
 - Bug in :meth:`Index.union` behaving differently depending on whether operand is a :class:`Index` or other list-like (:issue:`36384`)
 - Passing an array with 2 or more dimensions to the :class:`Series` constructor now raises the more specific ``ValueError``, from a bare ``Exception`` previously (:issue:`35744`)
 

pandas/core/strings/accessor.py

@@ -247,6 +247,8 @@ def _wrap_result(
         from pandas import Index, MultiIndex
 
         if not hasattr(result, "ndim") or not hasattr(result, "dtype"):
+            if isinstance(result, ABCDataFrame):
+                result = result.__finalize__(self._orig, name="str")
             return result
         assert result.ndim < 3
 
@@ -324,6 +326,11 @@ def cons_row(x):
                 # Must be a Series
                 cons = self._orig._constructor
                 result = cons(result, name=name, index=index)
+            result = result.__finalize__(self._orig, method="str")
+            if name is not None and result.ndim == 1:
+                # __finalize__ might copy over the original name, but we may
+                # want the new name (e.g. str.extract).
+                result.name = name
             return result
 
     def _get_series_list(self, others):
@@ -597,6 +604,7 @@ def cat(self, others=None, sep=None, na_rep=None, join="left"):
             else:
                 dtype = self._orig.dtype
             result = Series(result, dtype=dtype, index=data.index, name=self._orig.name)
+            result = result.__finalize__(self._orig, method="str_cat")
         return result
 
     _shared_docs[
@@ -3034,7 +3042,8 @@ def str_extract(arr, pat, flags=0, expand=True):
     if not isinstance(expand, bool):
         raise ValueError("expand must be True or False")
     if expand:
-        return _str_extract_frame(arr._orig, pat, flags=flags)
+        result = _str_extract_frame(arr._orig, pat, flags=flags)
+        return result.__finalize__(arr._orig, method="str_extract")
     else:
         result, name = _str_extract_noexpand(arr._orig, pat, flags=flags)
         return arr._wrap_result(result, name=name, expand=expand)

pandas/tests/generic/test_finalize.py

@@ -598,22 +598,13 @@ def test_binops(args, annotate, all_arithmetic_functions):
     [
         operator.methodcaller("capitalize"),
         operator.methodcaller("casefold"),
-        pytest.param(
-            operator.methodcaller("cat", ["a"]),
-            marks=pytest.mark.xfail(reason="finalize not called."),
-        ),
+        operator.methodcaller("cat", ["a"]),
         operator.methodcaller("contains", "a"),
         operator.methodcaller("count", "a"),
         operator.methodcaller("encode", "utf-8"),
         operator.methodcaller("endswith", "a"),
-        pytest.param(
-            operator.methodcaller("extract", r"(\w)(\d)"),
-            marks=pytest.mark.xfail(reason="finalize not called."),
-        ),
-        pytest.param(
-            operator.methodcaller("extract", r"(\w)(\d)"),
-            marks=pytest.mark.xfail(reason="finalize not called."),
-        ),
+        operator.methodcaller("extract", r"(\w)(\d)"),
+        operator.methodcaller("extract", r"(\w)(\d)", expand=False),
         operator.methodcaller("find", "a"),
         operator.methodcaller("findall", "a"),
         operator.methodcaller("get", 0),
@@ -655,7 +646,6 @@ def test_binops(args, annotate, all_arithmetic_functions):
     ],
     ids=idfn,
 )
-@not_implemented_mark
 def test_string_method(method):
     s = pd.Series(["a1"])
     s.attrs = {"a": 1}