BUG: fix replacer's dtypes not respected for frame replace (pandas-de…

…v#26632) (pandas-dev#29317)

doc/source/whatsnew/v1.0.0.rst

@@ -466,6 +466,7 @@ Reshaping
 - Better error message in :func:`get_dummies` when `columns` isn't a list-like value (:issue:`28383`)
 - Bug :meth:`Series.pct_change` where supplying an anchored frequency would throw a ValueError (:issue:`28664`)
 - Bug where :meth:`DataFrame.equals` returned True incorrectly in some cases when two DataFrames had the same columns in different orders (:issue:`28839`)
+- Bug in :meth:`DataFrame.replace` that caused non-numeric replacer's dtype not respected (:issue:`26632`)
 
 Sparse
 ^^^^^^

pandas/core/internals/blocks.py

@@ -2825,6 +2825,8 @@ def _replace_coerce(
             if convert:
                 block = [b.convert(numeric=False, copy=True) for b in block]
             return block
+        if convert:
+            return [self.convert(numeric=False, copy=True)]
         return self
 
 

pandas/core/internals/managers.py

@@ -629,7 +629,7 @@ def comp(s, regex=False):
                         convert=convert,
                         regex=regex,
                     )
-                    if m.any():
+                    if m.any() or convert:
                         new_rb = _extend_blocks(result, new_rb)
                     else:
                         new_rb.append(b)

pandas/tests/frame/test_replace.py

@@ -1338,5 +1338,21 @@ def test_replace_commutative(self, df, to_replace, exp):
 
         expected = pd.DataFrame(exp)
         result = df.replace(to_replace)
+        tm.assert_frame_equal(result, expected)
 
+    @pytest.mark.parametrize(
+        "replacer",
+        [
+            pd.Timestamp("20170827"),
+            np.int8(1),
+            np.int16(1),
+            np.float32(1),
+            np.float64(1),
+        ],
+    )
+    def test_replace_replacer_dtype(self, replacer):
+        # GH26632
+        df = pd.DataFrame(["a"])
+        result = df.replace({"a": replacer, "b": replacer})
+        expected = pd.DataFrame([replacer])
         tm.assert_frame_equal(result, expected)