BUG: Fix replacing in string series with NA (pandas-dev#32621)

pandas/core/internals/managers.py

@@ -1941,6 +1941,24 @@ def _compare_or_regex_search(a, b, regex=False):
     -------
     mask : array_like of bool
     """
+
+    def _check(result, a, b):
+        if is_scalar(result) and (
+            isinstance(a, np.ndarray) or isinstance(b, np.ndarray)
+        ):
+            type_names = [type(a).__name__, type(b).__name__]
+
+            if is_a_array:
+                type_names[0] = f"ndarray(dtype={a.dtype})"
+
+            if is_b_array:
+                type_names[1] = f"ndarray(dtype={b.dtype})"
+
+            raise TypeError(
+                f"Cannot compare types {repr(type_names[0])} and {repr(type_names[1])}"
+            )
+        return result
+
     if not regex:
         op = lambda x: operator.eq(x, b)
     else:
@@ -1951,25 +1969,29 @@ def _compare_or_regex_search(a, b, regex=False):
     is_a_array = isinstance(a, np.ndarray)
     is_b_array = isinstance(b, np.ndarray)
 
+    # GH#32621 use mask to avoid comparing to NAs
+    if is_a_array and not is_b_array:
+        mask = np.reshape(~(isna(a)), a.shape)
+    elif is_b_array and not is_a_array:
+        mask = np.reshape(~(isna(b)), b.shape)
+    elif is_a_array and is_b_array:
+        mask = ~(isna(a) | isna(b))
+    if is_a_array:
+        a = a[mask]
+    if is_b_array:
+        b = b[mask]
+
     if is_datetimelike_v_numeric(a, b) or is_numeric_v_string_like(a, b):
         # GH#29553 avoid deprecation warnings from numpy
-        result = False
+        return _check(False, a, b)
     else:
         result = op(a)
+        if isinstance(result, np.ndarray):
+            tmp = np.zeros(mask.shape, dtype=np.bool)
+            tmp[mask] = result
+            result = tmp
 
-    if is_scalar(result) and (is_a_array or is_b_array):
-        type_names = [type(a).__name__, type(b).__name__]
-
-        if is_a_array:
-            type_names[0] = f"ndarray(dtype={a.dtype})"
-
-        if is_b_array:
-            type_names[1] = f"ndarray(dtype={b.dtype})"
-
-        raise TypeError(
-            f"Cannot compare types {repr(type_names[0])} and {repr(type_names[1])}"
-        )
-    return result
+    return _check(result, a, b)
 
 
 def _fast_count_smallints(arr):

pandas/tests/series/methods/test_replace.py

@@ -241,6 +241,13 @@ def test_replace2(self):
         assert (ser[6:10] == -1).all()
         assert (ser[20:30] == -1).all()
 
+    def test_replace_with_dictlike_and_string_dtype(self):
+        # GH 32621
+        s = pd.Series(["one", "two", np.nan], dtype="string")
+        expected = pd.Series(["1", "2", np.nan])
+        result = s.replace({"one": "1", "two": "2"})
+        tm.assert_series_equal(expected, result)
+
     def test_replace_with_empty_dictlike(self):
         # GH 15289
         s = pd.Series(list("abcd"))