[backport 2.3.x] TST (string dtype): resolve xfails for frame fillna …

…and replace tests + fix bug in replace for string (#60295) (#60331)

* TST (string dtype): resolve xfails for frame fillna and replace tests + fix bug in replace for string (#60295)

(cherry picked from commit fae3e80)

* fix tests for default mode

* fixes

* cleanup

* update indexing tests

pandas/core/array_algos/replace.py

@@ -149,4 +149,6 @@ def re_replacer(s):
     if mask is None:
         values[:] = f(values)
     else:
+        if values.ndim != mask.ndim:
+            mask = np.broadcast_to(mask, values.shape)
         values[mask] = f(values[mask])

pandas/core/internals/blocks.py

@@ -929,7 +929,7 @@ def replace(
                     blocks = blk.convert(
                         copy=False,
                         using_cow=using_cow,
-                        convert_string=convert_string or self.dtype != _dtype_obj,
+                        convert_string=convert_string or self.dtype == "string",
                     )
                     if len(blocks) > 1 or blocks[0].dtype != blk.dtype:
                         warnings.warn(
@@ -987,7 +987,7 @@ def _replace_regex(
         inplace: bool = False,
         mask=None,
         using_cow: bool = False,
-        convert_string: bool = True,
+        convert_string=None,
         already_warned=None,
     ) -> list[Block]:
         """
@@ -1048,10 +1048,18 @@ def _replace_regex(
                 already_warned.warned_already = True
 
         nbs = block.convert(
-            copy=False, using_cow=using_cow, convert_string=convert_string
+            copy=False,
+            using_cow=using_cow,
+            convert_string=convert_string or self.dtype == "string",
         )
         opt = get_option("future.no_silent_downcasting")
-        if (len(nbs) > 1 or nbs[0].dtype != block.dtype) and not opt:
+        if (
+            len(nbs) > 1
+            or (
+                nbs[0].dtype != block.dtype
+                and not (self.dtype == "string" and nbs[0].dtype == "string")
+            )
+        ) and not opt:
             warnings.warn(
                 # GH#54710
                 "Downcasting behavior in `replace` is deprecated and "
@@ -1088,7 +1096,7 @@ def replace_list(
             values._replace(to_replace=src_list, value=dest_list, inplace=True)
             return [blk]
 
-        convert_string = self.dtype != _dtype_obj
+        convert_string = self.dtype == "string"
 
         # Exclude anything that we know we won't contain
         pairs = [
@@ -2167,6 +2175,13 @@ def where(
                 if isinstance(self.dtype, (IntervalDtype, StringDtype)):
                     # TestSetitemFloatIntervalWithIntIntervalValues
                     blk = self.coerce_to_target_dtype(orig_other)
+                    if (
+                        self.ndim == 2
+                        and isinstance(orig_cond, np.ndarray)
+                        and orig_cond.ndim == 1
+                        and not is_1d_only_ea_dtype(blk.dtype)
+                    ):
+                        orig_cond = orig_cond[:, None]
                     nbs = blk.where(orig_other, orig_cond, using_cow=using_cow)
                     return self._maybe_downcast(
                         nbs, downcast=_downcast, using_cow=using_cow, caller="where"

pandas/tests/frame/methods/test_fillna.py

@@ -1,8 +1,6 @@
 import numpy as np
 import pytest
 
-from pandas._config import using_string_dtype
-
 import pandas.util._test_decorators as td
 
 from pandas import (
@@ -91,8 +89,6 @@ def test_fillna_datetime(self, datetime_frame):
         with pytest.raises(ValueError, match=msg):
             datetime_frame.fillna(5, method="ffill")
 
-    # TODO(infer_string) test as actual error instead of xfail
-    @pytest.mark.xfail(using_string_dtype(), reason="can't fill 0 in string")
     def test_fillna_mixed_type(self, float_string_frame):
         mf = float_string_frame
         mf.loc[mf.index[5:20], "foo"] = np.nan
@@ -126,7 +122,7 @@ def test_fillna_empty(self, using_copy_on_write):
                 df.x.fillna(method=m, inplace=True)
                 df.x.fillna(method=m)
 
-    def test_fillna_different_dtype(self, using_infer_string):
+    def test_fillna_different_dtype(self):
         # with different dtype (GH#3386)
         df = DataFrame(
             [["a", "a", np.nan, "a"], ["b", "b", np.nan, "b"], ["c", "c", np.nan, "c"]]
@@ -136,6 +132,7 @@ def test_fillna_different_dtype(self, using_infer_string):
         expected = DataFrame(
             [["a", "a", "foo", "a"], ["b", "b", "foo", "b"], ["c", "c", "foo", "c"]]
         )
+        # column is originally float (all-NaN) -> filling with string gives object dtype
         expected[2] = expected[2].astype("object")
         tm.assert_frame_equal(result, expected)
 
@@ -654,18 +651,10 @@ def test_fillna_col_reordering(self):
             filled = df.fillna(method="ffill")
         assert df.columns.tolist() == filled.columns.tolist()
 
-    # TODO(infer_string) test as actual error instead of xfail
-    @pytest.mark.xfail(using_string_dtype(), reason="can't fill 0 in string")
-    def test_fill_corner(self, float_frame, float_string_frame):
-        mf = float_string_frame
-        mf.loc[mf.index[5:20], "foo"] = np.nan
-        mf.loc[mf.index[-10:], "A"] = np.nan
-
-        filled = float_string_frame.fillna(value=0)
-        assert (filled.loc[filled.index[5:20], "foo"] == 0).all()
-        del float_string_frame["foo"]
-
-        float_frame.reindex(columns=[]).fillna(value=0)
+    def test_fill_empty(self, float_frame):
+        df = float_frame.reindex(columns=[])
+        result = df.fillna(value=0)
+        tm.assert_frame_equal(result, df)
 
     def test_fillna_downcast_dict(self):
         # GH#40809

pandas/tests/frame/methods/test_replace.py

@@ -6,8 +6,6 @@
 import numpy as np
 import pytest
 
-from pandas._config import using_string_dtype
-
 import pandas as pd
 from pandas import (
     DataFrame,
@@ -30,7 +28,6 @@ def mix_abc() -> dict[str, list[float | str]]:
 
 
 class TestDataFrameReplace:
-    @pytest.mark.xfail(using_string_dtype(), reason="can't set float into string")
     def test_replace_inplace(self, datetime_frame, float_string_frame):
         datetime_frame.loc[datetime_frame.index[:5], "A"] = np.nan
         datetime_frame.loc[datetime_frame.index[-5:], "A"] = np.nan
@@ -46,7 +43,9 @@ def test_replace_inplace(self, datetime_frame, float_string_frame):
         mf.iloc[-10:, mf.columns.get_loc("A")] = np.nan
 
         result = float_string_frame.replace(np.nan, 0)
-        expected = float_string_frame.fillna(value=0)
+        expected = float_string_frame.copy()
+        expected["foo"] = expected["foo"].astype(object)
+        expected = expected.fillna(value=0)
         tm.assert_frame_equal(result, expected)
 
         tsframe = datetime_frame.copy()
@@ -290,34 +289,39 @@ def test_regex_replace_dict_nested_non_first_character(self, any_string_dtype):
         tm.assert_frame_equal(result, expected)
 
     def test_regex_replace_dict_nested_gh4115(self):
-        df = DataFrame({"Type": ["Q", "T", "Q", "Q", "T"], "tmp": 2})
+        df = DataFrame(
+            {"Type": Series(["Q", "T", "Q", "Q", "T"], dtype=object), "tmp": 2}
+        )
         expected = DataFrame({"Type": [0, 1, 0, 0, 1], "tmp": 2})
         msg = "Downcasting behavior in `replace`"
         with tm.assert_produces_warning(FutureWarning, match=msg):
             result = df.replace({"Type": {"Q": 0, "T": 1}})
+
         tm.assert_frame_equal(result, expected)
 
-    @pytest.mark.xfail(using_string_dtype(), reason="can't set float into string")
-    def test_regex_replace_list_to_scalar(self, mix_abc):
+    def test_regex_replace_list_to_scalar(self, mix_abc, using_infer_string):
         df = DataFrame(mix_abc)
         expec = DataFrame(
             {
                 "a": mix_abc["a"],
-                "b": np.array([np.nan] * 4),
+                "b": [np.nan] * 4,
                 "c": [np.nan, np.nan, np.nan, "d"],
             }
         )
+        if using_infer_string:
+            expec["b"] = expec["b"].astype("str")
         msg = "Downcasting behavior in `replace`"
-        with tm.assert_produces_warning(FutureWarning, match=msg):
+        warn = None if using_infer_string else FutureWarning
+        with tm.assert_produces_warning(warn, match=msg):
             res = df.replace([r"\s*\.\s*", "a|b"], np.nan, regex=True)
         res2 = df.copy()
         res3 = df.copy()
-        with tm.assert_produces_warning(FutureWarning, match=msg):
+        with tm.assert_produces_warning(warn, match=msg):
             return_value = res2.replace(
                 [r"\s*\.\s*", "a|b"], np.nan, regex=True, inplace=True
             )
         assert return_value is None
-        with tm.assert_produces_warning(FutureWarning, match=msg):
+        with tm.assert_produces_warning(warn, match=msg):
             return_value = res3.replace(
                 regex=[r"\s*\.\s*", "a|b"], value=np.nan, inplace=True
             )
@@ -326,7 +330,6 @@ def test_regex_replace_list_to_scalar(self, mix_abc):
         tm.assert_frame_equal(res2, expec)
         tm.assert_frame_equal(res3, expec)
 
-    @pytest.mark.xfail(using_string_dtype(), reason="can't set float into string")
     def test_regex_replace_str_to_numeric(self, mix_abc):
         # what happens when you try to replace a numeric value with a regex?
         df = DataFrame(mix_abc)
@@ -342,7 +345,6 @@ def test_regex_replace_str_to_numeric(self, mix_abc):
         tm.assert_frame_equal(res2, expec)
         tm.assert_frame_equal(res3, expec)
 
-    @pytest.mark.xfail(using_string_dtype(), reason="can't set float into string")
     def test_regex_replace_regex_list_to_numeric(self, mix_abc):
         df = DataFrame(mix_abc)
         res = df.replace([r"\s*\.\s*", "b"], 0, regex=True)
@@ -539,21 +541,28 @@ def test_replace_convert(self):
         res = rep.dtypes
         tm.assert_series_equal(expec, res)
 
-    @pytest.mark.xfail(using_string_dtype(), reason="can't set float into string")
     def test_replace_mixed(self, float_string_frame):
         mf = float_string_frame
         mf.iloc[5:20, mf.columns.get_loc("foo")] = np.nan
         mf.iloc[-10:, mf.columns.get_loc("A")] = np.nan
 
         result = float_string_frame.replace(np.nan, -18)
-        expected = float_string_frame.fillna(value=-18)
+        expected = float_string_frame.copy()
+        expected["foo"] = expected["foo"].astype(object)
+        expected = expected.fillna(value=-18)
         tm.assert_frame_equal(result, expected)
-        tm.assert_frame_equal(result.replace(-18, np.nan), float_string_frame)
+        expected2 = float_string_frame.copy()
+        expected2["foo"] = expected2["foo"].astype(object)
+        tm.assert_frame_equal(result.replace(-18, np.nan), expected2)
 
         result = float_string_frame.replace(np.nan, -1e8)
-        expected = float_string_frame.fillna(value=-1e8)
+        expected = float_string_frame.copy()
+        expected["foo"] = expected["foo"].astype(object)
+        expected = expected.fillna(value=-1e8)
         tm.assert_frame_equal(result, expected)
-        tm.assert_frame_equal(result.replace(-1e8, np.nan), float_string_frame)
+        expected2 = float_string_frame.copy()
+        expected2["foo"] = expected2["foo"].astype(object)
+        tm.assert_frame_equal(result.replace(-1e8, np.nan), expected2)
 
     def test_replace_mixed_int_block_upcasting(self):
         # int block upcasting
@@ -614,15 +623,11 @@ def test_replace_mixed2(self, using_infer_string):
 
         expected = DataFrame(
             {
-                "A": Series(["foo", "bar"]),
+                "A": Series(["foo", "bar"], dtype="object"),
                 "B": Series([0, "foo"], dtype="object"),
             }
         )
-        if using_infer_string:
-            with tm.assert_produces_warning(FutureWarning, match="Downcasting"):
-                result = df.replace([1, 2], ["foo", "bar"])
-        else:
-            result = df.replace([1, 2], ["foo", "bar"])
+        result = df.replace([1, 2], ["foo", "bar"])
         tm.assert_frame_equal(result, expected)
 
     def test_replace_mixed3(self):
@@ -931,15 +936,16 @@ def test_replace_limit(self):
         # TODO
         pass
 
-    def test_replace_dict_no_regex(self):
+    def test_replace_dict_no_regex(self, any_string_dtype):
         answer = Series(
             {
                 0: "Strongly Agree",
                 1: "Agree",
                 2: "Neutral",
                 3: "Disagree",
                 4: "Strongly Disagree",
-            }
+            },
+            dtype=any_string_dtype,
         )
         weights = {
             "Agree": 4,
@@ -954,15 +960,16 @@ def test_replace_dict_no_regex(self):
             result = answer.replace(weights)
         tm.assert_series_equal(result, expected)
 
-    def test_replace_series_no_regex(self):
+    def test_replace_series_no_regex(self, any_string_dtype):
         answer = Series(
             {
                 0: "Strongly Agree",
                 1: "Agree",
                 2: "Neutral",
                 3: "Disagree",
                 4: "Strongly Disagree",
-            }
+            },
+            dtype=any_string_dtype,
         )
         weights = Series(
             {
@@ -1060,16 +1067,15 @@ def test_nested_dict_overlapping_keys_replace_str(self):
         expected = df.replace({"a": dict(zip(astr, bstr))})
         tm.assert_frame_equal(result, expected)
 
-    @pytest.mark.xfail(using_string_dtype(), reason="can't set float into string")
-    def test_replace_swapping_bug(self, using_infer_string):
+    def test_replace_swapping_bug(self):
         df = DataFrame({"a": [True, False, True]})
         res = df.replace({"a": {True: "Y", False: "N"}})
-        expect = DataFrame({"a": ["Y", "N", "Y"]})
+        expect = DataFrame({"a": ["Y", "N", "Y"]}, dtype=object)
         tm.assert_frame_equal(res, expect)
 
         df = DataFrame({"a": [0, 1, 0]})
         res = df.replace({"a": {0: "Y", 1: "N"}})
-        expect = DataFrame({"a": ["Y", "N", "Y"]})
+        expect = DataFrame({"a": ["Y", "N", "Y"]}, dtype=object)
         tm.assert_frame_equal(res, expect)
 
     def test_replace_period(self):
@@ -1345,7 +1351,7 @@ def test_replace_commutative(self, df, to_replace, exp):
     )
     def test_replace_replacer_dtype(self, replacer):
         # GH26632
-        df = DataFrame(["a"])
+        df = DataFrame(["a"], dtype=object)
         msg = "Downcasting behavior in `replace` "
         with tm.assert_produces_warning(FutureWarning, match=msg):
             result = df.replace({"a": replacer, "b": replacer})
@@ -1462,6 +1468,7 @@ def test_replace_value_category_type(self):
             input_df = input_df.replace("obj1", "obj9")
             result = input_df.replace("cat2", "catX")
 
+        result = result.astype({"col1": "int64", "col3": "float64", "col5": "str"})
         tm.assert_frame_equal(result, expected)
 
     def test_replace_dict_category_type(self):
@@ -1503,13 +1510,11 @@ def test_replace_with_compiled_regex(self):
         expected = DataFrame(["z", "b", "c"])
         tm.assert_frame_equal(result, expected)
 
-    def test_replace_intervals(self, using_infer_string):
+    def test_replace_intervals(self):
         # https://github.com/pandas-dev/pandas/issues/35931
         df = DataFrame({"a": [pd.Interval(0, 1), pd.Interval(0, 1)]})
-        warning = FutureWarning if using_infer_string else None
-        with tm.assert_produces_warning(warning, match="Downcasting"):
-            result = df.replace({"a": {pd.Interval(0, 1): "x"}})
-        expected = DataFrame({"a": ["x", "x"]})
+        result = df.replace({"a": {pd.Interval(0, 1): "x"}})
+        expected = DataFrame({"a": ["x", "x"]}, dtype=object)
         tm.assert_frame_equal(result, expected)
 
     def test_replace_unicode(self):

pandas/tests/indexing/test_coercion.py

@@ -856,7 +856,7 @@ def test_replace_series(self, how, to_key, from_key, replacer, using_infer_strin
         else:
             exp = pd.Series(self.rep[to_key], index=index, name="yyy")
 
-        if using_infer_string and exp.dtype == "string" and obj.dtype == object:
+        if using_infer_string and exp.dtype == "string":
             # with infer_string, we disable the deprecated downcasting behavior
             exp = exp.astype(object)
 
@@ -889,8 +889,9 @@ def test_replace_series_datetime_tz(
         assert obj.dtype == from_key
 
         exp = pd.Series(self.rep[to_key], index=index, name="yyy")
-        if using_infer_string and to_key == "object":
-            assert exp.dtype == "string"
+        if using_infer_string and exp.dtype == "string":
+            # with infer_string, we disable the deprecated downcasting behavior
+            exp = exp.astype(object)
         else:
             assert exp.dtype == to_key