From 1470dd62488f200d9f972b492bb6bbe08fb38e8e Mon Sep 17 00:00:00 2001
From: phofl <patrick_hoefler@gmx.net>
Date: Thu, 26 Mar 2020 23:43:32 +0100
Subject: [PATCH 1/3] Fix unwanted type casting while replacing values in a
 DataFrame

---
 pandas/core/internals/blocks.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/pandas/core/internals/blocks.py b/pandas/core/internals/blocks.py
index a8cdb554edf03..660c70b64a961 100644
--- a/pandas/core/internals/blocks.py
+++ b/pandas/core/internals/blocks.py
@@ -734,7 +734,7 @@ def replace(
 
             # try again with a compatible block
             block = self.astype(object)
-            return block.replace(
+            block_replaced = block.replace(
                 to_replace=to_replace,
                 value=value,
                 inplace=inplace,
@@ -742,6 +742,9 @@ def replace(
                 regex=regex,
                 convert=convert,
             )
+            return [
+                inner_elem.convert() for elem in block_replaced for inner_elem in elem
+            ]
 
         values = self.values
         if lib.is_scalar(to_replace) and isinstance(values, np.ndarray):

From ec40b4117e2c0067e10dc113e83da036eb64011d Mon Sep 17 00:00:00 2001
From: phofl <patrick_hoefler@gmx.net>
Date: Fri, 27 Mar 2020 16:52:38 +0100
Subject: [PATCH 2/3] Add tests and fix small Bug

---
 pandas/core/internals/blocks.py            | 14 +++++++++++---
 pandas/tests/frame/methods/test_replace.py | 19 +++++++++++++++++++
 2 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/pandas/core/internals/blocks.py b/pandas/core/internals/blocks.py
index 660c70b64a961..1aa5d991124f7 100644
--- a/pandas/core/internals/blocks.py
+++ b/pandas/core/internals/blocks.py
@@ -742,9 +742,17 @@ def replace(
                 regex=regex,
                 convert=convert,
             )
-            return [
-                inner_elem.convert() for elem in block_replaced for inner_elem in elem
-            ]
+            blocks_converted = []
+            for ls_elem in block_replaced:
+                # If a replace was executed block_replaced is list of lists,
+                # if no replace was necessary block_replaced is only a list
+                if is_list_like(ls_elem):
+                    blocks_converted.extend(
+                        [sub_block.convert() for sub_block in ls_elem]
+                    )
+                else:
+                    blocks_converted.extend([ls_elem.convert()])
+            return blocks_converted
 
         values = self.values
         if lib.is_scalar(to_replace) and isinstance(values, np.ndarray):
diff --git a/pandas/tests/frame/methods/test_replace.py b/pandas/tests/frame/methods/test_replace.py
index ee89562261b19..1367df2203db1 100644
--- a/pandas/tests/frame/methods/test_replace.py
+++ b/pandas/tests/frame/methods/test_replace.py
@@ -22,6 +22,25 @@ def mix_abc() -> Dict[str, List[Union[float, str]]]:
 
 
 class TestDataFrameReplace:
+    def test_replace_without_type_cast(self):
+        # PH: 32988: Fix unwanted type casting while replacing
+        result = (
+            pd.DataFrame(np.eye(2))
+            .replace(to_replace=[None, -np.inf, np.inf], value=pd.NA)
+            .dtypes
+        )
+        expected = pd.Series([np.float64, np.float64])
+        tm.assert_series_equal(result, expected)
+
+        result = pd.DataFrame(np.eye(2)).replace(
+            to_replace=[None, -np.inf, np.inf, 1.0], value=pd.NA
+        )
+        expected_dtypes = pd.Series([np.float64, np.float64])
+
+        expected = pd.DataFrame({0: [np.nan, 0.0], 1: [0.0, np.nan]})
+        tm.assert_series_equal(result.dtypes, expected_dtypes)
+        tm.assert_frame_equal(result, expected)
+
     def test_replace_inplace(self, datetime_frame, float_string_frame):
         datetime_frame["A"][:5] = np.nan
         datetime_frame["A"][-5:] = np.nan

From 126d6d7cc73c49a767ff0370c8cceb0323ba010c Mon Sep 17 00:00:00 2001
From: phofl <patrick_hoefler@gmx.net>
Date: Fri, 27 Mar 2020 17:43:27 +0100
Subject: [PATCH 3/3] Change comparison from dtypes to values

---
 pandas/tests/frame/methods/test_replace.py | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/pandas/tests/frame/methods/test_replace.py b/pandas/tests/frame/methods/test_replace.py
index 1367df2203db1..c1035dc8cf2ab 100644
--- a/pandas/tests/frame/methods/test_replace.py
+++ b/pandas/tests/frame/methods/test_replace.py
@@ -24,21 +24,16 @@ def mix_abc() -> Dict[str, List[Union[float, str]]]:
 class TestDataFrameReplace:
     def test_replace_without_type_cast(self):
         # PH: 32988: Fix unwanted type casting while replacing
-        result = (
-            pd.DataFrame(np.eye(2))
-            .replace(to_replace=[None, -np.inf, np.inf], value=pd.NA)
-            .dtypes
+        result = pd.DataFrame(np.eye(2)).replace(
+            to_replace=[None, -np.inf, np.inf], value=pd.NA
         )
-        expected = pd.Series([np.float64, np.float64])
-        tm.assert_series_equal(result, expected)
+        tm.assert_frame_equal(result, pd.DataFrame(np.eye(2)))
 
         result = pd.DataFrame(np.eye(2)).replace(
             to_replace=[None, -np.inf, np.inf, 1.0], value=pd.NA
         )
-        expected_dtypes = pd.Series([np.float64, np.float64])
 
         expected = pd.DataFrame({0: [np.nan, 0.0], 1: [0.0, np.nan]})
-        tm.assert_series_equal(result.dtypes, expected_dtypes)
         tm.assert_frame_equal(result, expected)
 
     def test_replace_inplace(self, datetime_frame, float_string_frame):