From 9557eb9b61ddcebdaebb5c3fba9b892f4503abfa Mon Sep 17 00:00:00 2001
From: Joris Van den Bossche <jorisvandenbossche@gmail.com>
Date: Tue, 2 Mar 2021 09:12:13 +0100
Subject: [PATCH 1/2] REF: remove internal Block usage from FrameColumnApply

---
 pandas/core/apply.py              | 5 ++---
 pandas/core/internals/managers.py | 9 +++++++++
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/pandas/core/apply.py b/pandas/core/apply.py
index 15cee1419afb5..a4e8668f71909 100644
--- a/pandas/core/apply.py
+++ b/pandas/core/apply.py
@@ -883,9 +883,8 @@ def series_generator(self):
         #  of it.  Kids: don't do this at home.
         ser = self.obj._ixs(0, axis=0)
         mgr = ser._mgr
-        blk = mgr.blocks[0]
 
-        if is_extension_array_dtype(blk.dtype):
+        if is_extension_array_dtype(ser.dtype):
             # values will be incorrect for this block
             # TODO(EA2D): special case would be unnecessary with 2D EAs
             obj = self.obj
@@ -896,7 +895,7 @@ def series_generator(self):
             for (arr, name) in zip(values, self.index):
                 # GH#35462 re-pin mgr in case setitem changed it
                 ser._mgr = mgr
-                blk.values = arr
+                ser._mgr.set_values(arr)
                 ser.name = name
                 yield ser
 
diff --git a/pandas/core/internals/managers.py b/pandas/core/internals/managers.py
index e013a7f680d6f..4ceaf7cd3b6b5 100644
--- a/pandas/core/internals/managers.py
+++ b/pandas/core/internals/managers.py
@@ -1646,6 +1646,15 @@ def fast_xs(self, loc):
         """
         raise NotImplementedError("Use series._values[loc] instead")
 
+    def set_values(self, values):
+        """
+        Set the values of the single block in place.
+
+        Use at your own risk! This does not check if the passed values are
+        valid for the current Block/SingleBlockManager (length, dtype, etc).
+        """
+        self.blocks[0].values = values
+
 
 # --------------------------------------------------------------------
 # Constructor Helpers

From f82737d6fd74f0f196a54a6f56844d3bb28caa12 Mon Sep 17 00:00:00 2001
From: Joris Van den Bossche <jorisvandenbossche@gmail.com>
Date: Tue, 2 Mar 2021 17:09:59 +0100
Subject: [PATCH 2/2] update for comments

---
 pandas/core/apply.py              | 2 +-
 pandas/core/internals/managers.py | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/pandas/core/apply.py b/pandas/core/apply.py
index a4e8668f71909..203a0c675282d 100644
--- a/pandas/core/apply.py
+++ b/pandas/core/apply.py
@@ -895,7 +895,7 @@ def series_generator(self):
             for (arr, name) in zip(values, self.index):
                 # GH#35462 re-pin mgr in case setitem changed it
                 ser._mgr = mgr
-                ser._mgr.set_values(arr)
+                mgr.set_values(arr)
                 ser.name = name
                 yield ser
 
diff --git a/pandas/core/internals/managers.py b/pandas/core/internals/managers.py
index 4ceaf7cd3b6b5..2ad7471d6f086 100644
--- a/pandas/core/internals/managers.py
+++ b/pandas/core/internals/managers.py
@@ -1646,7 +1646,7 @@ def fast_xs(self, loc):
         """
         raise NotImplementedError("Use series._values[loc] instead")
 
-    def set_values(self, values):
+    def set_values(self, values: ArrayLike):
         """
         Set the values of the single block in place.