From b3e1bc5100d7620375b37334ac1c87d9a74473ea Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Thu, 13 Oct 2022 02:53:01 -0700
Subject: [PATCH 01/41] Add `BZ2File` wrapper for pickle protocol 5

---
 pandas/io/common.py | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/pandas/io/common.py b/pandas/io/common.py
index 4d324b009d1e3..ff63fb2327c59 100644
--- a/pandas/io/common.py
+++ b/pandas/io/common.py
@@ -22,6 +22,7 @@
 import mmap
 import os
 from pathlib import Path
+from pickle import PickleBuffer
 import re
 import tarfile
 from typing import (
@@ -762,9 +763,9 @@ def get_handle(
 
         # BZ Compression
         elif compression == "bz2":
-            # No overload variant of "BZ2File" matches argument types
+            # Overload of "BZ2File" to handle pickle protocol 5
             # "Union[str, BaseBuffer]", "str", "Dict[str, Any]"
-            handle = bz2.BZ2File(  # type: ignore[call-overload]
+            handle = _BZ2File(  # type: ignore[call-overload]
                 handle,
                 mode=ioargs.mode,
                 **compression_args,
@@ -1002,6 +1003,22 @@ def write_to_buffer(self) -> None:
         self.buffer.addfile(tarinfo, self)
 
 
+class _BZ2File(bz2.BZ2File):
+    def write(self, b) -> int:
+        if isinstance(b, PickleBuffer):
+            # Workaround issue where `bz2.BZ2File` expects `len`
+            # to return the number of bytes in `b` by converting
+            # `b` into something that meets that constraint with
+            # minimal copying.
+            try:
+                # coerce to 1-D `uint8` C-contiguous `memoryview` zero-copy
+                b = b.raw()
+            except BufferError:
+                # perform in-memory copy if buffer is not contiguous
+                b = bytes(b)
+        return super().write(b)
+
+
 class _BytesZipFile(_BufferedWriter):
     def __init__(
         self,

From 17f725b6cc15bf5a773201e57742ceeca772de46 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Thu, 13 Oct 2022 02:53:01 -0700
Subject: [PATCH 02/41] Add `LZMAFile` wrapper for pickle protocol 5

---
 pandas/compat/__init__.py | 38 +++++++++++++++++++++++++++++---------
 1 file changed, 29 insertions(+), 9 deletions(-)

diff --git a/pandas/compat/__init__.py b/pandas/compat/__init__.py
index 80f66c945ba27..86551516521d8 100644
--- a/pandas/compat/__init__.py
+++ b/pandas/compat/__init__.py
@@ -10,9 +10,16 @@
 from __future__ import annotations
 
 import os
+from pickle import PickleBuffer
 import platform
 import sys
-from typing import TYPE_CHECKING
+
+try:
+    import lzma
+
+    has_lzma = True
+except ImportError:
+    has_lzma = False
 
 from pandas._typing import F
 from pandas.compat.numpy import (
@@ -31,9 +38,6 @@
     pa_version_under9p0,
 )
 
-if TYPE_CHECKING:
-    import lzma
-
 PY39 = sys.version_info >= (3, 9)
 PY310 = sys.version_info >= (3, 10)
 PY311 = sys.version_info >= (3, 11)
@@ -41,6 +45,24 @@
 IS64 = sys.maxsize > 2**32
 
 
+if has_lzma:
+
+    class _LZMAFile(lzma.LZMAFile):
+        def write(self, b) -> int:
+            if isinstance(b, PickleBuffer):
+                # Workaround issue where `lzma.LZMAFile` expects `len`
+                # to return the number of bytes in `b` by converting
+                # `b` into something that meets that constraint with
+                # minimal copying.
+                try:
+                    # coerce to 1-D `uint8` C-contiguous `memoryview` zero-copy
+                    b = b.raw()
+                except BufferError:
+                    # perform in-memory copy if buffer is not contiguous
+                    b = bytes(b)
+            return super().write(b)
+
+
 def set_function_name(f: F, name: str, cls) -> F:
     """
     Bind the name/qualname attributes of the function.
@@ -126,7 +148,7 @@ def is_ci_environment() -> bool:
     return os.environ.get("PANDAS_CI", "0") == "1"
 
 
-def get_lzma_file() -> type[lzma.LZMAFile]:
+def get_lzma_file() -> type[_LZMAFile]:
     """
     Importing the `LZMAFile` class from the `lzma` module.
 
@@ -140,15 +162,13 @@ def get_lzma_file() -> type[lzma.LZMAFile]:
     RuntimeError
         If the `lzma` module was not imported correctly, or didn't exist.
     """
-    try:
-        import lzma
-    except ImportError:
+    if not has_lzma:
         raise RuntimeError(
             "lzma module not available. "
             "A Python re-install with the proper dependencies, "
             "might be required to solve this issue."
         )
-    return lzma.LZMAFile
+    return _LZMAFile
 
 
 __all__ = [

From 280731e76a8224cff89cfed19755b3b50b1172b6 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Thu, 13 Oct 2022 02:53:02 -0700
Subject: [PATCH 03/41] Use BZ2 & LZMA wrappers for full pickle support

---
 pandas/io/pickle.py | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/pandas/io/pickle.py b/pandas/io/pickle.py
index 373d608876c3e..1d720b881525b 100644
--- a/pandas/io/pickle.py
+++ b/pandas/io/pickle.py
@@ -101,15 +101,8 @@ def to_pickle(
         is_text=False,
         storage_options=storage_options,
     ) as handles:
-        if handles.compression["method"] in ("bz2", "xz") and protocol >= 5:
-            # some weird TypeError GH#39002 with pickle 5: fallback to letting
-            # pickle create the entire object and then write it to the buffer.
-            # "zip" would also be here if pandas.io.common._BytesZipFile
-            # wouldn't buffer write calls
-            handles.handle.write(pickle.dumps(obj, protocol=protocol))
-        else:
-            # letting pickle write directly to the buffer is more memory-efficient
-            pickle.dump(obj, handles.handle, protocol=protocol)
+        # letting pickle write directly to the buffer is more memory-efficient
+        pickle.dump(obj, handles.handle, protocol=protocol)
 
 
 @doc(

From ccda94ea37b0fbd8c311ba17b28b007d01892062 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Thu, 13 Oct 2022 03:58:05 -0700
Subject: [PATCH 04/41] Workaround linter issue

`PickleBuffer` isn't currently included in `SupportBytes`, which causes
issues with pyright when passing `PickleBuffer` instances to `bytes`.
Though it appears ok passing `PickleBuffer` instances to `memoryview`s.
So do that instead. This is functionaly very equivalent. There is a
slight performance cost to making a `memoryview`, but this is likely
negligible compared to copying to `bytes`.
---
 pandas/compat/__init__.py | 2 +-
 pandas/io/common.py       | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/pandas/compat/__init__.py b/pandas/compat/__init__.py
index 86551516521d8..494453b5f8ff2 100644
--- a/pandas/compat/__init__.py
+++ b/pandas/compat/__init__.py
@@ -59,7 +59,7 @@ def write(self, b) -> int:
                     b = b.raw()
                 except BufferError:
                     # perform in-memory copy if buffer is not contiguous
-                    b = bytes(b)
+                    b = memoryview(b).tobytes()
             return super().write(b)
 
 
diff --git a/pandas/io/common.py b/pandas/io/common.py
index ff63fb2327c59..4b0fbe1f9b1f9 100644
--- a/pandas/io/common.py
+++ b/pandas/io/common.py
@@ -1015,7 +1015,7 @@ def write(self, b) -> int:
                 b = b.raw()
             except BufferError:
                 # perform in-memory copy if buffer is not contiguous
-                b = bytes(b)
+                b = memoryview(b).tobytes()
         return super().write(b)
 
 

From 08c37e5a0ac648ed6477a1ad8c3082330ccef6e7 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 03:15:49 -0700
Subject: [PATCH 05/41] Refactor out `flatten_buffer`

---
 pandas/compat/__init__.py      | 24 +++---------------------
 pandas/compat/lzma.py          | 18 ++++++++++++++++++
 pandas/compat/pickle_compat.py | 22 ++++++++++++++++++++++
 pandas/io/common.py            | 18 ++++++------------
 4 files changed, 49 insertions(+), 33 deletions(-)
 create mode 100644 pandas/compat/lzma.py

diff --git a/pandas/compat/__init__.py b/pandas/compat/__init__.py
index 494453b5f8ff2..be38ed125eb6a 100644
--- a/pandas/compat/__init__.py
+++ b/pandas/compat/__init__.py
@@ -15,7 +15,7 @@
 import sys
 
 try:
-    import lzma
+    import pandas.compat.lzma
 
     has_lzma = True
 except ImportError:
@@ -45,24 +45,6 @@
 IS64 = sys.maxsize > 2**32
 
 
-if has_lzma:
-
-    class _LZMAFile(lzma.LZMAFile):
-        def write(self, b) -> int:
-            if isinstance(b, PickleBuffer):
-                # Workaround issue where `lzma.LZMAFile` expects `len`
-                # to return the number of bytes in `b` by converting
-                # `b` into something that meets that constraint with
-                # minimal copying.
-                try:
-                    # coerce to 1-D `uint8` C-contiguous `memoryview` zero-copy
-                    b = b.raw()
-                except BufferError:
-                    # perform in-memory copy if buffer is not contiguous
-                    b = memoryview(b).tobytes()
-            return super().write(b)
-
-
 def set_function_name(f: F, name: str, cls) -> F:
     """
     Bind the name/qualname attributes of the function.
@@ -148,7 +130,7 @@ def is_ci_environment() -> bool:
     return os.environ.get("PANDAS_CI", "0") == "1"
 
 
-def get_lzma_file() -> type[_LZMAFile]:
+def get_lzma_file() -> type[pandas.compat.lzma.LZMAFile]:
     """
     Importing the `LZMAFile` class from the `lzma` module.
 
@@ -168,7 +150,7 @@ def get_lzma_file() -> type[_LZMAFile]:
             "A Python re-install with the proper dependencies, "
             "might be required to solve this issue."
         )
-    return _LZMAFile
+    return pandas.compat.lzma.LZMAFile
 
 
 __all__ = [
diff --git a/pandas/compat/lzma.py b/pandas/compat/lzma.py
new file mode 100644
index 0000000000000..7105c7da6191f
--- /dev/null
+++ b/pandas/compat/lzma.py
@@ -0,0 +1,18 @@
+"""
+Patched ``LZMAFile`` to handle pickle protocol 5.
+"""
+
+from __future__ import annotations
+
+import lzma
+
+from pandas.compat.pickle_compat import flatten_buffer
+
+
+class LZMAFile(lzma.LZMAFile):
+    def write(self, b) -> int:
+        # Workaround issue where `lzma.LZMAFile` expects `len`
+        # to return the number of bytes in `b` by converting
+        # `b` into something that meets that constraint with
+        # minimal copying.
+        return super().write(flatten_buffer(b))
diff --git a/pandas/compat/pickle_compat.py b/pandas/compat/pickle_compat.py
index c233e3d8a4892..f9a52d5dd5e47 100644
--- a/pandas/compat/pickle_compat.py
+++ b/pandas/compat/pickle_compat.py
@@ -33,6 +33,28 @@
     )
 
 
+def flatten_buffer(b: bytes | bytearray | memoryview | pkl.PickleBuffer):
+    """
+    Return some 1-D `uint8` typed buffer.
+
+    Coerces anything that does not match that description to one that does
+    without copying if possible (otherwise will copy).
+    """
+
+    if isinstance(b, (bytes, bytearray)):
+        return b
+
+    if not isinstance(b, pkl.PickleBuffer):
+        b = pkl.PickleBuffer(b)
+
+    try:
+        # coerce to 1-D `uint8` C-contiguous `memoryview` zero-copy
+        return b.raw()
+    except BufferError:
+        # perform in-memory copy if buffer is not contiguous
+        return memoryview(b).tobytes()
+
+
 def load_reduce(self):
     stack = self.stack
     args = stack.pop()
diff --git a/pandas/io/common.py b/pandas/io/common.py
index 4b0fbe1f9b1f9..107971523725e 100644
--- a/pandas/io/common.py
+++ b/pandas/io/common.py
@@ -57,6 +57,7 @@
     WriteBuffer,
 )
 from pandas.compat import get_lzma_file
+from pandas.compat.pickle_compat import flatten_buffer
 from pandas.compat._optional import import_optional_dependency
 from pandas.util._decorators import doc
 from pandas.util._exceptions import find_stack_level
@@ -1005,18 +1006,11 @@ def write_to_buffer(self) -> None:
 
 class _BZ2File(bz2.BZ2File):
     def write(self, b) -> int:
-        if isinstance(b, PickleBuffer):
-            # Workaround issue where `bz2.BZ2File` expects `len`
-            # to return the number of bytes in `b` by converting
-            # `b` into something that meets that constraint with
-            # minimal copying.
-            try:
-                # coerce to 1-D `uint8` C-contiguous `memoryview` zero-copy
-                b = b.raw()
-            except BufferError:
-                # perform in-memory copy if buffer is not contiguous
-                b = memoryview(b).tobytes()
-        return super().write(b)
+        # Workaround issue where `bz2.BZ2File` expects `len`
+        # to return the number of bytes in `b` by converting
+        # `b` into something that meets that constraint with
+        # minimal copying.
+        return super().write(flatten_buffer(b))
 
 
 class _BytesZipFile(_BufferedWriter):

From 8109338ba1e6fd3d2d222adf39e764e4b1dc6b3a Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 03:16:24 -0700
Subject: [PATCH 06/41] Refactor `B2File` into separate module

---
 pandas/compat/bz2.py | 18 ++++++++++++++++++
 pandas/io/common.py  | 12 +-----------
 2 files changed, 19 insertions(+), 11 deletions(-)
 create mode 100644 pandas/compat/bz2.py

diff --git a/pandas/compat/bz2.py b/pandas/compat/bz2.py
new file mode 100644
index 0000000000000..1ce0986c1176d
--- /dev/null
+++ b/pandas/compat/bz2.py
@@ -0,0 +1,18 @@
+"""
+Patched ``BZ2File`` to handle pickle protocol 5.
+"""
+
+from __future__ import annotations
+
+import bz2
+
+from pandas.compat.pickle_compat import flatten_buffer
+
+
+class BZ2File(bz2.BZ2File):
+    def write(self, b) -> int:
+        # Workaround issue where `bz2.BZ2File` expects `len`
+        # to return the number of bytes in `b` by converting
+        # `b` into something that meets that constraint with
+        # minimal copying.
+        return super().write(flatten_buffer(b))
diff --git a/pandas/io/common.py b/pandas/io/common.py
index 107971523725e..3cf46d6c2f99a 100644
--- a/pandas/io/common.py
+++ b/pandas/io/common.py
@@ -5,7 +5,6 @@
     ABC,
     abstractmethod,
 )
-import bz2
 import codecs
 import dataclasses
 import functools
@@ -57,7 +56,7 @@
     WriteBuffer,
 )
 from pandas.compat import get_lzma_file
-from pandas.compat.pickle_compat import flatten_buffer
+from pandas.compat.bz2 import BZ2File as _BZ2File
 from pandas.compat._optional import import_optional_dependency
 from pandas.util._decorators import doc
 from pandas.util._exceptions import find_stack_level
@@ -1004,15 +1003,6 @@ def write_to_buffer(self) -> None:
         self.buffer.addfile(tarinfo, self)
 
 
-class _BZ2File(bz2.BZ2File):
-    def write(self, b) -> int:
-        # Workaround issue where `bz2.BZ2File` expects `len`
-        # to return the number of bytes in `b` by converting
-        # `b` into something that meets that constraint with
-        # minimal copying.
-        return super().write(flatten_buffer(b))
-
-
 class _BytesZipFile(_BufferedWriter):
     def __init__(
         self,

From 691eba789667a3992f57efe0fe440a5227c639e7 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 03:31:54 -0700
Subject: [PATCH 07/41] Test `flatten_buffer`

This provides a reasonable proxy for testing patched `BZ2File` and
`LZMAFile` objects.
---
 pandas/tests/io/test_pickle.py | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/pandas/tests/io/test_pickle.py b/pandas/tests/io/test_pickle.py
index 98f02e14f4f13..167224025bd0c 100644
--- a/pandas/tests/io/test_pickle.py
+++ b/pandas/tests/io/test_pickle.py
@@ -10,6 +10,7 @@
 
 3. Move the created pickle to "data/legacy_pickle/<version>" directory.
 """
+from array import array
 import bz2
 import datetime
 import functools
@@ -38,6 +39,7 @@
     is_platform_little_endian,
 )
 from pandas.compat._optional import import_optional_dependency
+from pandas.compat.pickle import flatten_buffer
 import pandas.util._test_decorators as td
 
 import pandas as pd
@@ -105,6 +107,26 @@ def legacy_pickle(request, datapath):
 # ---------------------
 # tests
 # ---------------------
+
+
+@pytest.mark.parametrize(
+    "data",
+    [
+        b"123",
+        b"123456",
+        bytearray(b"123"),
+        memoryview(b"123"),
+        pickle.PickleBuffer(b"123"),
+        array("I", [1, 2, 3]),
+        memoryview(b"123456").cast("B", (3, 2)),
+        memoryview(b"123456").cast("B", (3, 2))[::2],
+    ],
+)
+def test_flatten_buffer(data):
+    result = flatten_buffer(data)
+    assert result == bytes(data)
+
+
 def test_pickles(legacy_pickle):
     if not is_platform_little_endian():
         pytest.skip("known failure on non-little endian")

From 7a93b704157fcb8f730b89d3d77a653b3f65ab0a Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 03:39:37 -0700
Subject: [PATCH 08/41] Move `flatten_buffer` to `_utils`

This ran into cyclic import issues in `pickle_compat`. So move
`flatten_buffer` to its own module free of these issues.
---
 pandas/compat/_utils.py        | 27 +++++++++++++++++++++++++++
 pandas/compat/bz2.py           |  2 +-
 pandas/compat/lzma.py          |  2 +-
 pandas/compat/pickle_compat.py | 22 ----------------------
 pandas/tests/io/test_pickle.py |  2 +-
 5 files changed, 30 insertions(+), 25 deletions(-)
 create mode 100644 pandas/compat/_utils.py

diff --git a/pandas/compat/_utils.py b/pandas/compat/_utils.py
new file mode 100644
index 0000000000000..4ed2a47f98869
--- /dev/null
+++ b/pandas/compat/_utils.py
@@ -0,0 +1,27 @@
+"""
+Utilities used in various `compat` components.
+"""
+
+import pickle
+
+
+def flatten_buffer(b: bytes | bytearray | memoryview | pickle.PickleBuffer):
+    """
+    Return some 1-D `uint8` typed buffer.
+
+    Coerces anything that does not match that description to one that does
+    without copying if possible (otherwise will copy).
+    """
+
+    if isinstance(b, (bytes, bytearray)):
+        return b
+
+    if not isinstance(b, pickle.PickleBuffer):
+        b = pickle.PickleBuffer(b)
+
+    try:
+        # coerce to 1-D `uint8` C-contiguous `memoryview` zero-copy
+        return b.raw()
+    except BufferError:
+        # perform in-memory copy if buffer is not contiguous
+        return memoryview(b).tobytes()
diff --git a/pandas/compat/bz2.py b/pandas/compat/bz2.py
index 1ce0986c1176d..dcf2915342cd0 100644
--- a/pandas/compat/bz2.py
+++ b/pandas/compat/bz2.py
@@ -6,7 +6,7 @@
 
 import bz2
 
-from pandas.compat.pickle_compat import flatten_buffer
+from pandas.compat._utils import flatten_buffer
 
 
 class BZ2File(bz2.BZ2File):
diff --git a/pandas/compat/lzma.py b/pandas/compat/lzma.py
index 7105c7da6191f..49d80b754c970 100644
--- a/pandas/compat/lzma.py
+++ b/pandas/compat/lzma.py
@@ -6,7 +6,7 @@
 
 import lzma
 
-from pandas.compat.pickle_compat import flatten_buffer
+from pandas.compat._utils import flatten_buffer
 
 
 class LZMAFile(lzma.LZMAFile):
diff --git a/pandas/compat/pickle_compat.py b/pandas/compat/pickle_compat.py
index f9a52d5dd5e47..c233e3d8a4892 100644
--- a/pandas/compat/pickle_compat.py
+++ b/pandas/compat/pickle_compat.py
@@ -33,28 +33,6 @@
     )
 
 
-def flatten_buffer(b: bytes | bytearray | memoryview | pkl.PickleBuffer):
-    """
-    Return some 1-D `uint8` typed buffer.
-
-    Coerces anything that does not match that description to one that does
-    without copying if possible (otherwise will copy).
-    """
-
-    if isinstance(b, (bytes, bytearray)):
-        return b
-
-    if not isinstance(b, pkl.PickleBuffer):
-        b = pkl.PickleBuffer(b)
-
-    try:
-        # coerce to 1-D `uint8` C-contiguous `memoryview` zero-copy
-        return b.raw()
-    except BufferError:
-        # perform in-memory copy if buffer is not contiguous
-        return memoryview(b).tobytes()
-
-
 def load_reduce(self):
     stack = self.stack
     args = stack.pop()
diff --git a/pandas/tests/io/test_pickle.py b/pandas/tests/io/test_pickle.py
index 167224025bd0c..73f8fec1a68cf 100644
--- a/pandas/tests/io/test_pickle.py
+++ b/pandas/tests/io/test_pickle.py
@@ -39,7 +39,7 @@
     is_platform_little_endian,
 )
 from pandas.compat._optional import import_optional_dependency
-from pandas.compat.pickle import flatten_buffer
+from pandas.compat._utils import flatten_buffer
 import pandas.util._test_decorators as td
 
 import pandas as pd

From 8f5b0a1ed9647d4ba7cbb79545c0e6c7be77faf2 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 03:53:16 -0700
Subject: [PATCH 09/41] Import `annotations` to fix `|` usage

---
 pandas/compat/_utils.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/pandas/compat/_utils.py b/pandas/compat/_utils.py
index 4ed2a47f98869..83f4c7f8ee382 100644
--- a/pandas/compat/_utils.py
+++ b/pandas/compat/_utils.py
@@ -2,6 +2,8 @@
 Utilities used in various `compat` components.
 """
 
+from __future__ import annotations
+
 import pickle
 
 

From c54529a9a91ada16744c955817ad936c8d0faad8 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 11:54:42 -0700
Subject: [PATCH 10/41] Sort `import`s to fix lint

---
 pandas/io/common.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/io/common.py b/pandas/io/common.py
index e9158794f9f33..43a9a1e7448a3 100644
--- a/pandas/io/common.py
+++ b/pandas/io/common.py
@@ -55,8 +55,8 @@
     WriteBuffer,
 )
 from pandas.compat import get_lzma_file
-from pandas.compat.bz2 import BZ2File as _BZ2File
 from pandas.compat._optional import import_optional_dependency
+from pandas.compat.bz2 import BZ2File as _BZ2File
 from pandas.util._decorators import doc
 from pandas.util._exceptions import find_stack_level
 

From 7604d48da0c72985ab4a6d98e4c77368ecca5f14 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 12:00:24 -0700
Subject: [PATCH 11/41] Patch `BZ2File` & `LZMAFile` on Python pre-3.10

This should limit the effects of this patch. Also should make it easier
to remove this backport later once all supported Python versions have
the fix.
---
 pandas/compat/bz2.py  | 21 ++++++++++++++-------
 pandas/compat/lzma.py | 21 ++++++++++++++-------
 2 files changed, 28 insertions(+), 14 deletions(-)

diff --git a/pandas/compat/bz2.py b/pandas/compat/bz2.py
index dcf2915342cd0..db0767c361801 100644
--- a/pandas/compat/bz2.py
+++ b/pandas/compat/bz2.py
@@ -5,14 +5,21 @@
 from __future__ import annotations
 
 import bz2
+import sys
 
 from pandas.compat._utils import flatten_buffer
 
 
-class BZ2File(bz2.BZ2File):
-    def write(self, b) -> int:
-        # Workaround issue where `bz2.BZ2File` expects `len`
-        # to return the number of bytes in `b` by converting
-        # `b` into something that meets that constraint with
-        # minimal copying.
-        return super().write(flatten_buffer(b))
+if sys.version_info < (3, 10):
+    class BZ2File(bz2.BZ2File):
+        def write(self, b) -> int:
+            # Workaround issue where `bz2.BZ2File` expects `len`
+            # to return the number of bytes in `b` by converting
+            # `b` into something that meets that constraint with
+            # minimal copying.
+            #
+            # Note: This is fixed in Python 3.10.
+            return super().write(flatten_buffer(b))
+else:
+    class BZ2File(bz2.BZ2File):
+        pass
diff --git a/pandas/compat/lzma.py b/pandas/compat/lzma.py
index 49d80b754c970..4ce27c5ab845c 100644
--- a/pandas/compat/lzma.py
+++ b/pandas/compat/lzma.py
@@ -5,14 +5,21 @@
 from __future__ import annotations
 
 import lzma
+import sys
 
 from pandas.compat._utils import flatten_buffer
 
 
-class LZMAFile(lzma.LZMAFile):
-    def write(self, b) -> int:
-        # Workaround issue where `lzma.LZMAFile` expects `len`
-        # to return the number of bytes in `b` by converting
-        # `b` into something that meets that constraint with
-        # minimal copying.
-        return super().write(flatten_buffer(b))
+if sys.version_info < (3, 10):
+    class LZMAFile(lzma.LZMAFile):
+        def write(self, b) -> int:
+            # Workaround issue where `lzma.LZMAFile` expects `len`
+            # to return the number of bytes in `b` by converting
+            # `b` into something that meets that constraint with
+            # minimal copying.
+            #
+            # Note: This is fixed in Python 3.10.
+            return super().write(flatten_buffer(b))
+else:
+    class LZMAFile(lzma.LZMAFile):
+        pass

From 9f3d38712d565a14fd27ac92696264036a353c22 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 12:05:12 -0700
Subject: [PATCH 12/41] Test C & F contiguous NumPy arrays

Also test another non-contiguous array.
---
 pandas/tests/io/test_pickle.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/pandas/tests/io/test_pickle.py b/pandas/tests/io/test_pickle.py
index 73f8fec1a68cf..f7fbdd8234c94 100644
--- a/pandas/tests/io/test_pickle.py
+++ b/pandas/tests/io/test_pickle.py
@@ -120,6 +120,9 @@ def legacy_pickle(request, datapath):
         array("I", [1, 2, 3]),
         memoryview(b"123456").cast("B", (3, 2)),
         memoryview(b"123456").cast("B", (3, 2))[::2],
+        np.arange(12).reshape((3, 4), order="C"),
+        np.arange(12).reshape((3, 4), order="F"),
+        np.arange(12).reshape((3, 4), order="C")[:, ::2],
     ],
 )
 def test_flatten_buffer(data):

From 16f21a5078650c8a80828951794ed6a78282bfae Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 12:11:22 -0700
Subject: [PATCH 13/41] Test `memoryview` is 1-D `uint8` contiguous data

If a `memoryview` is returned, make sure it as close to `bytes` |
`bytearray` as possible. This ensures if other functions assume
something like `bytes` (for example assuming `len(b)` is the number of
bytes contained), things will continue to work even though this is a
`memoryview`.
---
 pandas/tests/io/test_pickle.py | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/pandas/tests/io/test_pickle.py b/pandas/tests/io/test_pickle.py
index f7fbdd8234c94..51f78c893a4d1 100644
--- a/pandas/tests/io/test_pickle.py
+++ b/pandas/tests/io/test_pickle.py
@@ -128,6 +128,11 @@ def legacy_pickle(request, datapath):
 def test_flatten_buffer(data):
     result = flatten_buffer(data)
     assert result == bytes(data)
+    if isinstance(result, memoryview):
+        assert result.ndim == 1
+        assert result.format == "B"
+        assert result.contiguous
+        assert result.shape == (result.nbytes,)
 
 
 def test_pickles(legacy_pickle):

From 6df7e081270142afbfb738f26ab7763017a4cbfe Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 13:10:03 -0700
Subject: [PATCH 14/41] Run `black` on `bz2` and `lzma` compat files

---
 pandas/compat/bz2.py  | 3 +++
 pandas/compat/lzma.py | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/pandas/compat/bz2.py b/pandas/compat/bz2.py
index db0767c361801..7f1d4e8247341 100644
--- a/pandas/compat/bz2.py
+++ b/pandas/compat/bz2.py
@@ -11,6 +11,7 @@
 
 
 if sys.version_info < (3, 10):
+
     class BZ2File(bz2.BZ2File):
         def write(self, b) -> int:
             # Workaround issue where `bz2.BZ2File` expects `len`
@@ -20,6 +21,8 @@ def write(self, b) -> int:
             #
             # Note: This is fixed in Python 3.10.
             return super().write(flatten_buffer(b))
+
 else:
+
     class BZ2File(bz2.BZ2File):
         pass
diff --git a/pandas/compat/lzma.py b/pandas/compat/lzma.py
index 4ce27c5ab845c..922e9dc255936 100644
--- a/pandas/compat/lzma.py
+++ b/pandas/compat/lzma.py
@@ -11,6 +11,7 @@
 
 
 if sys.version_info < (3, 10):
+
     class LZMAFile(lzma.LZMAFile):
         def write(self, b) -> int:
             # Workaround issue where `lzma.LZMAFile` expects `len`
@@ -20,6 +21,8 @@ def write(self, b) -> int:
             #
             # Note: This is fixed in Python 3.10.
             return super().write(flatten_buffer(b))
+
 else:
+
     class LZMAFile(lzma.LZMAFile):
         pass

From 39ffab0c8416ca542a03a38ad5a665bce63012fc Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 13:41:42 -0700
Subject: [PATCH 15/41] One more lint fix

---
 pandas/compat/bz2.py  | 1 -
 pandas/compat/lzma.py | 1 -
 2 files changed, 2 deletions(-)

diff --git a/pandas/compat/bz2.py b/pandas/compat/bz2.py
index 7f1d4e8247341..f6dae95fed2a2 100644
--- a/pandas/compat/bz2.py
+++ b/pandas/compat/bz2.py
@@ -9,7 +9,6 @@
 
 from pandas.compat._utils import flatten_buffer
 
-
 if sys.version_info < (3, 10):
 
     class BZ2File(bz2.BZ2File):
diff --git a/pandas/compat/lzma.py b/pandas/compat/lzma.py
index 922e9dc255936..d5762790cbd89 100644
--- a/pandas/compat/lzma.py
+++ b/pandas/compat/lzma.py
@@ -9,7 +9,6 @@
 
 from pandas.compat._utils import flatten_buffer
 
-
 if sys.version_info < (3, 10):
 
     class LZMAFile(lzma.LZMAFile):

From f134dee7c1e6dff939489fbf324bdb8c88547032 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 14:06:42 -0700
Subject: [PATCH 16/41] Drop unused `PickleBuffer` `import`s

---
 pandas/compat/__init__.py | 1 -
 pandas/io/common.py       | 1 -
 2 files changed, 2 deletions(-)

diff --git a/pandas/compat/__init__.py b/pandas/compat/__init__.py
index 1c4dcb6004fa0..451ba9b9b00bd 100644
--- a/pandas/compat/__init__.py
+++ b/pandas/compat/__init__.py
@@ -10,7 +10,6 @@
 from __future__ import annotations
 
 import os
-from pickle import PickleBuffer
 import platform
 import sys
 
diff --git a/pandas/io/common.py b/pandas/io/common.py
index 43a9a1e7448a3..549daf97cea79 100644
--- a/pandas/io/common.py
+++ b/pandas/io/common.py
@@ -20,7 +20,6 @@
 import mmap
 import os
 from pathlib import Path
-from pickle import PickleBuffer
 import re
 import tarfile
 from typing import (

From a7126a28d3502caa5e26dde37b5b970233d0471e Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 14:34:01 -0700
Subject: [PATCH 17/41] Simplify change to `panda.compat.__init__`

Now that the LZMA changes are in a separate file, cleanup the changes to
`pandas.compat.__init__`.
---
 pandas/compat/__init__.py | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/pandas/compat/__init__.py b/pandas/compat/__init__.py
index 451ba9b9b00bd..3e6e4874e6b49 100644
--- a/pandas/compat/__init__.py
+++ b/pandas/compat/__init__.py
@@ -12,13 +12,7 @@
 import os
 import platform
 import sys
-
-try:
-    import pandas.compat.lzma
-
-    has_lzma = True
-except ImportError:
-    has_lzma = False
+from typing import TYPE_CHECKING
 
 from pandas._typing import F
 from pandas.compat.numpy import (
@@ -32,6 +26,9 @@
     pa_version_under9p0,
 )
 
+if TYPE_CHECKING:
+    import pandas.compat.lzma
+
 PY39 = sys.version_info >= (3, 9)
 PY310 = sys.version_info >= (3, 10)
 PY311 = sys.version_info >= (3, 11)
@@ -138,7 +135,9 @@ def get_lzma_file() -> type[pandas.compat.lzma.LZMAFile]:
     RuntimeError
         If the `lzma` module was not imported correctly, or didn't exist.
     """
-    if not has_lzma:
+    try:
+        import pandas.compat.lzma
+    except ImportError:
         raise RuntimeError(
             "lzma module not available. "
             "A Python re-install with the proper dependencies, "

From df7b0cef478d4aaaf47511e6788d949fc3e6ff4c Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 14:56:38 -0700
Subject: [PATCH 18/41] Type `flatten_buffer` result

---
 pandas/compat/_utils.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/pandas/compat/_utils.py b/pandas/compat/_utils.py
index 83f4c7f8ee382..f30573eb7a7e4 100644
--- a/pandas/compat/_utils.py
+++ b/pandas/compat/_utils.py
@@ -7,7 +7,9 @@
 import pickle
 
 
-def flatten_buffer(b: bytes | bytearray | memoryview | pickle.PickleBuffer):
+def flatten_buffer(
+    b: bytes | bytearray | memoryview | pickle.PickleBuffer,
+) -> bytes | memoryview:
     """
     Return some 1-D `uint8` typed buffer.
 

From 742788fcb5c6ae659086dc2046d0bb1fffc686e3 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 16:57:23 -0700
Subject: [PATCH 19/41] Use `order="A"` in `memoryview.tobytes(...)`

In the function `flatten_buffer`, the order is already effectively
enforced when copying can be avoided by using `PickleBuffer.raw(...)`.
However some test comparisons failed (when they shouldn't have) as this
wasn't specified. So add the `order` in both the function and the test.
This should fix that test failure.
---
 pandas/compat/_utils.py        | 2 +-
 pandas/tests/io/test_pickle.py | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/pandas/compat/_utils.py b/pandas/compat/_utils.py
index f30573eb7a7e4..9b686718f20d4 100644
--- a/pandas/compat/_utils.py
+++ b/pandas/compat/_utils.py
@@ -28,4 +28,4 @@ def flatten_buffer(
         return b.raw()
     except BufferError:
         # perform in-memory copy if buffer is not contiguous
-        return memoryview(b).tobytes()
+        return memoryview(b).tobytes("A")
diff --git a/pandas/tests/io/test_pickle.py b/pandas/tests/io/test_pickle.py
index 51f78c893a4d1..e8a3c1c972833 100644
--- a/pandas/tests/io/test_pickle.py
+++ b/pandas/tests/io/test_pickle.py
@@ -127,7 +127,8 @@ def legacy_pickle(request, datapath):
 )
 def test_flatten_buffer(data):
     result = flatten_buffer(data)
-    assert result == bytes(data)
+    expected = memoryview(data).tobytes("A")
+    assert result == expected
     if isinstance(result, memoryview):
         assert result.ndim == 1
         assert result.format == "B"

From ffc58d3c9081066850c403262fbd0a808fe74cff Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 17:08:21 -0700
Subject: [PATCH 20/41] Move all compat compressors into a single file

---
 pandas/compat/__init__.py      | 13 ++----
 pandas/compat/_compressors.py  | 78 ++++++++++++++++++++++++++++++++++
 pandas/compat/_utils.py        | 31 --------------
 pandas/compat/bz2.py           | 27 ------------
 pandas/compat/lzma.py          | 27 ------------
 pandas/tests/io/test_pickle.py |  2 +-
 6 files changed, 83 insertions(+), 95 deletions(-)
 create mode 100644 pandas/compat/_compressors.py
 delete mode 100644 pandas/compat/_utils.py
 delete mode 100644 pandas/compat/bz2.py
 delete mode 100644 pandas/compat/lzma.py

diff --git a/pandas/compat/__init__.py b/pandas/compat/__init__.py
index 3e6e4874e6b49..09100cfc388d6 100644
--- a/pandas/compat/__init__.py
+++ b/pandas/compat/__init__.py
@@ -12,9 +12,9 @@
 import os
 import platform
 import sys
-from typing import TYPE_CHECKING
 
 from pandas._typing import F
+import pandas.compat._compressors
 from pandas.compat.numpy import (
     is_numpy_dev,
     np_version_under1p21,
@@ -26,9 +26,6 @@
     pa_version_under9p0,
 )
 
-if TYPE_CHECKING:
-    import pandas.compat.lzma
-
 PY39 = sys.version_info >= (3, 9)
 PY310 = sys.version_info >= (3, 10)
 PY311 = sys.version_info >= (3, 11)
@@ -121,7 +118,7 @@ def is_ci_environment() -> bool:
     return os.environ.get("PANDAS_CI", "0") == "1"
 
 
-def get_lzma_file() -> type[pandas.compat.lzma.LZMAFile]:
+def get_lzma_file() -> type[pandas.compat._compressors.LZMAFile]:
     """
     Importing the `LZMAFile` class from the `lzma` module.
 
@@ -135,15 +132,13 @@ def get_lzma_file() -> type[pandas.compat.lzma.LZMAFile]:
     RuntimeError
         If the `lzma` module was not imported correctly, or didn't exist.
     """
-    try:
-        import pandas.compat.lzma
-    except ImportError:
+    if not pandas.compat._compressors.has_lzma:
         raise RuntimeError(
             "lzma module not available. "
             "A Python re-install with the proper dependencies, "
             "might be required to solve this issue."
         )
-    return pandas.compat.lzma.LZMAFile
+    return pandas.compat._compressors.LZMAFile
 
 
 __all__ = [
diff --git a/pandas/compat/_compressors.py b/pandas/compat/_compressors.py
new file mode 100644
index 0000000000000..94cd20750bb1b
--- /dev/null
+++ b/pandas/compat/_compressors.py
@@ -0,0 +1,78 @@
+"""
+Patched ``BZ2File`` and ``LZMAFile`` to handle pickle protocol 5.
+"""
+
+from __future__ import annotations
+
+import bz2
+import pickle
+import sys
+
+try:
+    import lzma
+
+    has_lzma = True
+except ImportError:
+    has_lzma = False
+
+
+PY310 = sys.version_info >= (3, 10)
+
+
+def flatten_buffer(
+    b: bytes | bytearray | memoryview | pickle.PickleBuffer,
+) -> bytes | memoryview:
+    """
+    Return some 1-D `uint8` typed buffer.
+
+    Coerces anything that does not match that description to one that does
+    without copying if possible (otherwise will copy).
+    """
+
+    if isinstance(b, (bytes, bytearray)):
+        return b
+
+    if not isinstance(b, pickle.PickleBuffer):
+        b = pickle.PickleBuffer(b)
+
+    try:
+        # coerce to 1-D `uint8` C-contiguous `memoryview` zero-copy
+        return b.raw()
+    except BufferError:
+        # perform in-memory copy if buffer is not contiguous
+        return memoryview(b).tobytes("A")
+
+
+if not PY310:
+
+    class BZ2File(bz2.BZ2File):
+        def write(self, b) -> int:
+            # Workaround issue where `bz2.BZ2File` expects `len`
+            # to return the number of bytes in `b` by converting
+            # `b` into something that meets that constraint with
+            # minimal copying.
+            #
+            # Note: This is fixed in Python 3.10.
+            return super().write(flatten_buffer(b))
+
+    if has_lzma:
+
+        class LZMAFile(lzma.LZMAFile):
+            def write(self, b) -> int:
+                # Workaround issue where `lzma.LZMAFile` expects `len`
+                # to return the number of bytes in `b` by converting
+                # `b` into something that meets that constraint with
+                # minimal copying.
+                #
+                # Note: This is fixed in Python 3.10.
+                return super().write(flatten_buffer(b))
+
+else:
+
+    class BZ2File(bz2.BZ2File):
+        pass
+
+    if has_lzma:
+
+        class LZMAFile(lzma.LZMAFile):
+            pass
diff --git a/pandas/compat/_utils.py b/pandas/compat/_utils.py
deleted file mode 100644
index 9b686718f20d4..0000000000000
--- a/pandas/compat/_utils.py
+++ /dev/null
@@ -1,31 +0,0 @@
-"""
-Utilities used in various `compat` components.
-"""
-
-from __future__ import annotations
-
-import pickle
-
-
-def flatten_buffer(
-    b: bytes | bytearray | memoryview | pickle.PickleBuffer,
-) -> bytes | memoryview:
-    """
-    Return some 1-D `uint8` typed buffer.
-
-    Coerces anything that does not match that description to one that does
-    without copying if possible (otherwise will copy).
-    """
-
-    if isinstance(b, (bytes, bytearray)):
-        return b
-
-    if not isinstance(b, pickle.PickleBuffer):
-        b = pickle.PickleBuffer(b)
-
-    try:
-        # coerce to 1-D `uint8` C-contiguous `memoryview` zero-copy
-        return b.raw()
-    except BufferError:
-        # perform in-memory copy if buffer is not contiguous
-        return memoryview(b).tobytes("A")
diff --git a/pandas/compat/bz2.py b/pandas/compat/bz2.py
deleted file mode 100644
index f6dae95fed2a2..0000000000000
--- a/pandas/compat/bz2.py
+++ /dev/null
@@ -1,27 +0,0 @@
-"""
-Patched ``BZ2File`` to handle pickle protocol 5.
-"""
-
-from __future__ import annotations
-
-import bz2
-import sys
-
-from pandas.compat._utils import flatten_buffer
-
-if sys.version_info < (3, 10):
-
-    class BZ2File(bz2.BZ2File):
-        def write(self, b) -> int:
-            # Workaround issue where `bz2.BZ2File` expects `len`
-            # to return the number of bytes in `b` by converting
-            # `b` into something that meets that constraint with
-            # minimal copying.
-            #
-            # Note: This is fixed in Python 3.10.
-            return super().write(flatten_buffer(b))
-
-else:
-
-    class BZ2File(bz2.BZ2File):
-        pass
diff --git a/pandas/compat/lzma.py b/pandas/compat/lzma.py
deleted file mode 100644
index d5762790cbd89..0000000000000
--- a/pandas/compat/lzma.py
+++ /dev/null
@@ -1,27 +0,0 @@
-"""
-Patched ``LZMAFile`` to handle pickle protocol 5.
-"""
-
-from __future__ import annotations
-
-import lzma
-import sys
-
-from pandas.compat._utils import flatten_buffer
-
-if sys.version_info < (3, 10):
-
-    class LZMAFile(lzma.LZMAFile):
-        def write(self, b) -> int:
-            # Workaround issue where `lzma.LZMAFile` expects `len`
-            # to return the number of bytes in `b` by converting
-            # `b` into something that meets that constraint with
-            # minimal copying.
-            #
-            # Note: This is fixed in Python 3.10.
-            return super().write(flatten_buffer(b))
-
-else:
-
-    class LZMAFile(lzma.LZMAFile):
-        pass
diff --git a/pandas/tests/io/test_pickle.py b/pandas/tests/io/test_pickle.py
index e8a3c1c972833..da688a74d77cf 100644
--- a/pandas/tests/io/test_pickle.py
+++ b/pandas/tests/io/test_pickle.py
@@ -38,8 +38,8 @@
     get_lzma_file,
     is_platform_little_endian,
 )
+from pandas.compat._compressors import flatten_buffer
 from pandas.compat._optional import import_optional_dependency
-from pandas.compat._utils import flatten_buffer
 import pandas.util._test_decorators as td
 
 import pandas as pd

From 0b1be1634eacd42ec666c1a0a741f53b4cad4741 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 17:23:58 -0700
Subject: [PATCH 21/41] Fix `BZ2File` `import`

---
 pandas/io/common.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/io/common.py b/pandas/io/common.py
index 549daf97cea79..64e703572f2bf 100644
--- a/pandas/io/common.py
+++ b/pandas/io/common.py
@@ -54,8 +54,8 @@
     WriteBuffer,
 )
 from pandas.compat import get_lzma_file
+from pandas.compat._compressors import BZ2File as _BZ2File
 from pandas.compat._optional import import_optional_dependency
-from pandas.compat.bz2 import BZ2File as _BZ2File
 from pandas.util._decorators import doc
 from pandas.util._exceptions import find_stack_level
 

From f00740ce89aa5efe75b348b6b9bacaa81909253b Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 17:40:58 -0700
Subject: [PATCH 22/41] Refactor out common compat constants

---
 pandas/compat/__init__.py     |  6 +-----
 pandas/compat/_compressors.py |  5 ++---
 pandas/compat/_constants.py   | 17 +++++++++++++++++
 3 files changed, 20 insertions(+), 8 deletions(-)
 create mode 100644 pandas/compat/_constants.py

diff --git a/pandas/compat/__init__.py b/pandas/compat/__init__.py
index 09100cfc388d6..56baf4b81efe5 100644
--- a/pandas/compat/__init__.py
+++ b/pandas/compat/__init__.py
@@ -26,11 +26,7 @@
     pa_version_under9p0,
 )
 
-PY39 = sys.version_info >= (3, 9)
-PY310 = sys.version_info >= (3, 10)
-PY311 = sys.version_info >= (3, 11)
-PYPY = platform.python_implementation() == "PyPy"
-IS64 = sys.maxsize > 2**32
+from pandas.compat._constants import *
 
 
 def set_function_name(f: F, name: str, cls) -> F:
diff --git a/pandas/compat/_compressors.py b/pandas/compat/_compressors.py
index 94cd20750bb1b..6df7b8bb66041 100644
--- a/pandas/compat/_compressors.py
+++ b/pandas/compat/_compressors.py
@@ -8,6 +8,8 @@
 import pickle
 import sys
 
+from pandas.compat._constants import PY310
+
 try:
     import lzma
 
@@ -16,9 +18,6 @@
     has_lzma = False
 
 
-PY310 = sys.version_info >= (3, 10)
-
-
 def flatten_buffer(
     b: bytes | bytearray | memoryview | pickle.PickleBuffer,
 ) -> bytes | memoryview:
diff --git a/pandas/compat/_constants.py b/pandas/compat/_constants.py
new file mode 100644
index 0000000000000..02b636106db99
--- /dev/null
+++ b/pandas/compat/_constants.py
@@ -0,0 +1,17 @@
+"""
+_constants
+======
+
+Constants relevant for the Python implementation.
+"""
+
+from __future__ import annotations
+
+import sys
+import platform
+
+PY39 = sys.version_info >= (3, 9)
+PY310 = sys.version_info >= (3, 10)
+PY311 = sys.version_info >= (3, 11)
+PYPY = platform.python_implementation() == "PyPy"
+IS64 = sys.maxsize > 2**32

From 06e5387398426a6dffc827f4eb587625d33b82b3 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 18:04:50 -0700
Subject: [PATCH 23/41] Fix `import` sorting

---
 pandas/compat/__init__.py   | 3 +--
 pandas/compat/_constants.py | 2 +-
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/pandas/compat/__init__.py b/pandas/compat/__init__.py
index 56baf4b81efe5..d5affb12075ff 100644
--- a/pandas/compat/__init__.py
+++ b/pandas/compat/__init__.py
@@ -15,6 +15,7 @@
 
 from pandas._typing import F
 import pandas.compat._compressors
+from pandas.compat._constants import *
 from pandas.compat.numpy import (
     is_numpy_dev,
     np_version_under1p21,
@@ -26,8 +27,6 @@
     pa_version_under9p0,
 )
 
-from pandas.compat._constants import *
-
 
 def set_function_name(f: F, name: str, cls) -> F:
     """
diff --git a/pandas/compat/_constants.py b/pandas/compat/_constants.py
index 02b636106db99..15bb3109e1971 100644
--- a/pandas/compat/_constants.py
+++ b/pandas/compat/_constants.py
@@ -7,8 +7,8 @@
 
 from __future__ import annotations
 
-import sys
 import platform
+import sys
 
 PY39 = sys.version_info >= (3, 9)
 PY310 = sys.version_info >= (3, 10)

From 269dc0f53f0022a8db055f3cd858c7251bce66d6 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 18:07:37 -0700
Subject: [PATCH 24/41] Drop unused `import`

---
 pandas/compat/_compressors.py | 1 -
 1 file changed, 1 deletion(-)

diff --git a/pandas/compat/_compressors.py b/pandas/compat/_compressors.py
index 6df7b8bb66041..66ac17178e030 100644
--- a/pandas/compat/_compressors.py
+++ b/pandas/compat/_compressors.py
@@ -6,7 +6,6 @@
 
 import bz2
 import pickle
-import sys
 
 from pandas.compat._constants import PY310
 

From f1f1a2e56861abbc0b2c04adbb98880794c47ca0 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 18:09:03 -0700
Subject: [PATCH 25/41] Ignore `flake8` errors on wildcard `import`

---
 pandas/compat/__init__.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/compat/__init__.py b/pandas/compat/__init__.py
index d5affb12075ff..0b2462dac7095 100644
--- a/pandas/compat/__init__.py
+++ b/pandas/compat/__init__.py
@@ -15,7 +15,7 @@
 
 from pandas._typing import F
 import pandas.compat._compressors
-from pandas.compat._constants import *
+from pandas.compat._constants import *  # noqa: F401,F403
 from pandas.compat.numpy import (
     is_numpy_dev,
     np_version_under1p21,

From f73f0a590ce94f112bcc5af587197e1ea79a6e63 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 18:27:19 -0700
Subject: [PATCH 26/41] Revert "Ignore `flake8` errors on wildcard `import`"

This reverts commit f1f1a2e56861abbc0b2c04adbb98880794c47ca0.
---
 pandas/compat/__init__.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/compat/__init__.py b/pandas/compat/__init__.py
index 0b2462dac7095..d5affb12075ff 100644
--- a/pandas/compat/__init__.py
+++ b/pandas/compat/__init__.py
@@ -15,7 +15,7 @@
 
 from pandas._typing import F
 import pandas.compat._compressors
-from pandas.compat._constants import *  # noqa: F401,F403
+from pandas.compat._constants import *
 from pandas.compat.numpy import (
     is_numpy_dev,
     np_version_under1p21,

From b8a724b5abd60384077531e2ef654b938f7a76a4 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 18:48:54 -0700
Subject: [PATCH 27/41] Explicitly `import` all constants

---
 pandas/compat/__init__.py | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/pandas/compat/__init__.py b/pandas/compat/__init__.py
index d5affb12075ff..7f4be8dae5452 100644
--- a/pandas/compat/__init__.py
+++ b/pandas/compat/__init__.py
@@ -15,7 +15,13 @@
 
 from pandas._typing import F
 import pandas.compat._compressors
-from pandas.compat._constants import *
+from pandas.compat._constants import (
+    IS64,
+    PY39,
+    PY310,
+    PY311,
+    PYPY,
+)
 from pandas.compat.numpy import (
     is_numpy_dev,
     np_version_under1p21,

From 1b111887cff577f22074c3327cf08087bdc3195c Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 18:49:24 -0700
Subject: [PATCH 28/41] Assign `IS64` first

---
 pandas/compat/_constants.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/pandas/compat/_constants.py b/pandas/compat/_constants.py
index 15bb3109e1971..cad5b8fc9b861 100644
--- a/pandas/compat/_constants.py
+++ b/pandas/compat/_constants.py
@@ -10,8 +10,9 @@
 import platform
 import sys
 
+IS64 = sys.maxsize > 2**32
+
 PY39 = sys.version_info >= (3, 9)
 PY310 = sys.version_info >= (3, 10)
 PY311 = sys.version_info >= (3, 11)
 PYPY = platform.python_implementation() == "PyPy"
-IS64 = sys.maxsize > 2**32

From d2a39db631bd29af1343eeb0c44765cb96917ae1 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 18:52:12 -0700
Subject: [PATCH 29/41] Try `noqa` on wildcard `import` again

---
 pandas/compat/__init__.py | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/pandas/compat/__init__.py b/pandas/compat/__init__.py
index 7f4be8dae5452..b019eb634541f 100644
--- a/pandas/compat/__init__.py
+++ b/pandas/compat/__init__.py
@@ -15,13 +15,7 @@
 
 from pandas._typing import F
 import pandas.compat._compressors
-from pandas.compat._constants import (
-    IS64,
-    PY39,
-    PY310,
-    PY311,
-    PYPY,
-)
+from pandas.compat._constants import *  # noqa: F401, F403
 from pandas.compat.numpy import (
     is_numpy_dev,
     np_version_under1p21,

From 01e86046534d5194fa38f0c8747128a260f65d32 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 19:36:28 -0700
Subject: [PATCH 30/41] Declare `BZ2File` & `LZMAFile` once

Fixes a linter issue from pyright.
---
 pandas/compat/_compressors.py | 21 +++++++--------------
 1 file changed, 7 insertions(+), 14 deletions(-)

diff --git a/pandas/compat/_compressors.py b/pandas/compat/_compressors.py
index 66ac17178e030..a8316aea6d28e 100644
--- a/pandas/compat/_compressors.py
+++ b/pandas/compat/_compressors.py
@@ -41,9 +41,9 @@ def flatten_buffer(
         return memoryview(b).tobytes("A")
 
 
-if not PY310:
+class BZ2File(bz2.BZ2File):
+    if not PY310:
 
-    class BZ2File(bz2.BZ2File):
         def write(self, b) -> int:
             # Workaround issue where `bz2.BZ2File` expects `len`
             # to return the number of bytes in `b` by converting
@@ -53,9 +53,12 @@ def write(self, b) -> int:
             # Note: This is fixed in Python 3.10.
             return super().write(flatten_buffer(b))
 
-    if has_lzma:
 
-        class LZMAFile(lzma.LZMAFile):
+if has_lzma:
+
+    class LZMAFile(lzma.LZMAFile):
+        if not PY310:
+
             def write(self, b) -> int:
                 # Workaround issue where `lzma.LZMAFile` expects `len`
                 # to return the number of bytes in `b` by converting
@@ -64,13 +67,3 @@ def write(self, b) -> int:
                 #
                 # Note: This is fixed in Python 3.10.
                 return super().write(flatten_buffer(b))
-
-else:
-
-    class BZ2File(bz2.BZ2File):
-        pass
-
-    if has_lzma:
-
-        class LZMAFile(lzma.LZMAFile):
-            pass

From 523e20c9efafff39a048939b0c1131341a92ccde Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 19:52:16 -0700
Subject: [PATCH 31/41] `import PickleBuffer` for simplicity

---
 pandas/compat/_compressors.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/pandas/compat/_compressors.py b/pandas/compat/_compressors.py
index a8316aea6d28e..3ae473d830823 100644
--- a/pandas/compat/_compressors.py
+++ b/pandas/compat/_compressors.py
@@ -5,7 +5,7 @@
 from __future__ import annotations
 
 import bz2
-import pickle
+from pickle import PickleBuffer
 
 from pandas.compat._constants import PY310
 
@@ -18,7 +18,7 @@
 
 
 def flatten_buffer(
-    b: bytes | bytearray | memoryview | pickle.PickleBuffer,
+    b: bytes | bytearray | memoryview | PickleBuffer,
 ) -> bytes | memoryview:
     """
     Return some 1-D `uint8` typed buffer.
@@ -30,8 +30,8 @@ def flatten_buffer(
     if isinstance(b, (bytes, bytearray)):
         return b
 
-    if not isinstance(b, pickle.PickleBuffer):
-        b = pickle.PickleBuffer(b)
+    if not isinstance(b, PickleBuffer):
+        b = PickleBuffer(b)
 
     try:
         # coerce to 1-D `uint8` C-contiguous `memoryview` zero-copy

From 6f7e29380cf21ad8a0adb86879b7c3c3124dfd09 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 19:53:26 -0700
Subject: [PATCH 32/41] Add `bytearray` to return type

---
 pandas/compat/_compressors.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/compat/_compressors.py b/pandas/compat/_compressors.py
index 3ae473d830823..a4f39c4e34bd4 100644
--- a/pandas/compat/_compressors.py
+++ b/pandas/compat/_compressors.py
@@ -19,7 +19,7 @@
 
 def flatten_buffer(
     b: bytes | bytearray | memoryview | PickleBuffer,
-) -> bytes | memoryview:
+) -> bytes | bytearray | memoryview:
     """
     Return some 1-D `uint8` typed buffer.
 

From 4614bd7f7d87d054cef5edc0382e2c0701453fd9 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Tue, 18 Oct 2022 19:55:11 -0700
Subject: [PATCH 33/41] Test `bytes` & `bytearray` are returned unaltered

---
 pandas/tests/io/test_pickle.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/pandas/tests/io/test_pickle.py b/pandas/tests/io/test_pickle.py
index da688a74d77cf..d78cb9e46cd1a 100644
--- a/pandas/tests/io/test_pickle.py
+++ b/pandas/tests/io/test_pickle.py
@@ -129,7 +129,9 @@ def test_flatten_buffer(data):
     result = flatten_buffer(data)
     expected = memoryview(data).tobytes("A")
     assert result == expected
-    if isinstance(result, memoryview):
+    if isinstance(data, (bytes, bytearray)):
+        assert result is data
+    elif isinstance(result, memoryview):
         assert result.ndim == 1
         assert result.format == "B"
         assert result.contiguous

From cf4f9262f78dd5bdfd655cecdb450aa7d816e209 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Wed, 19 Oct 2022 17:04:39 -0700
Subject: [PATCH 34/41] Explicit list all constants

---
 pandas/compat/__init__.py | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/pandas/compat/__init__.py b/pandas/compat/__init__.py
index b019eb634541f..2b545a4ba034e 100644
--- a/pandas/compat/__init__.py
+++ b/pandas/compat/__init__.py
@@ -15,7 +15,13 @@
 
 from pandas._typing import F
 import pandas.compat._compressors
-from pandas.compat._constants import *  # noqa: F401, F403
+from pandas.compat._constants import (  # noqa: F401
+    IS64,
+    PY39,
+    PY310,
+    PY311,
+    PYPY,
+)
 from pandas.compat.numpy import (
     is_numpy_dev,
     np_version_under1p21,

From 4a2efad9b04450005145f689c3f0d839334bff65 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Wed, 19 Oct 2022 18:32:55 -0700
Subject: [PATCH 35/41] Trick linter into thinking constants are used ;)

---
 pandas/compat/__init__.py | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/pandas/compat/__init__.py b/pandas/compat/__init__.py
index 2b545a4ba034e..8524654002e22 100644
--- a/pandas/compat/__init__.py
+++ b/pandas/compat/__init__.py
@@ -15,12 +15,12 @@
 
 from pandas._typing import F
 import pandas.compat._compressors
-from pandas.compat._constants import (  # noqa: F401
-    IS64,
-    PY39,
-    PY310,
-    PY311,
-    PYPY,
+from pandas.compat._constants import (
+    IS64 as IS64,
+    PY39 as PY39,
+    PY310 as PY310,
+    PY311 as PY311,
+    PYPY as PYPY,
 )
 from pandas.compat.numpy import (
     is_numpy_dev,

From 0dae47659fbc017683acfb695b3b6a4bfb9b1a6a Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Wed, 19 Oct 2022 18:35:57 -0700
Subject: [PATCH 36/41] Add new entry to 2.0.0

---
 doc/source/whatsnew/v2.0.0.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/doc/source/whatsnew/v2.0.0.rst b/doc/source/whatsnew/v2.0.0.rst
index 30acc117c237a..6d145004e380b 100644
--- a/doc/source/whatsnew/v2.0.0.rst
+++ b/doc/source/whatsnew/v2.0.0.rst
@@ -170,6 +170,7 @@ Performance improvements
 - Performance improvement in :func:`merge` and :meth:`DataFrame.join` when joining on a sorted :class:`MultiIndex` (:issue:`48504`)
 - Performance improvement in :meth:`DataFrame.loc` and :meth:`Series.loc` for tuple-based indexing of a :class:`MultiIndex` (:issue:`48384`)
 - Performance improvement for :meth:`MultiIndex.unique` (:issue:`48335`)
+- Performance use out-of-band pickling with BZ2 & LZMA files (:issue:`49068`)
 - Performance improvement for :class:`~arrays.StringArray` constructor passing a numpy array with type ``np.str_`` (:issue:`49109`)
 - Performance improvement in :meth:`~arrays.ArrowExtensionArray.factorize` (:issue:`49177`)
 - Performance improvement for :func:`concat` with extension array backed indexes (:issue:`49128`)

From 366f645e6f0f71401619d432d15582393169d1ca Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Wed, 19 Oct 2022 22:34:36 -0700
Subject: [PATCH 37/41] Assign constants to themselves

Should work around linter issues.
---
 pandas/compat/__init__.py | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/pandas/compat/__init__.py b/pandas/compat/__init__.py
index 8524654002e22..83a75ff4a6d67 100644
--- a/pandas/compat/__init__.py
+++ b/pandas/compat/__init__.py
@@ -16,11 +16,11 @@
 from pandas._typing import F
 import pandas.compat._compressors
 from pandas.compat._constants import (
-    IS64 as IS64,
-    PY39 as PY39,
-    PY310 as PY310,
-    PY311 as PY311,
-    PYPY as PYPY,
+    IS64,
+    PY39,
+    PY310,
+    PY311,
+    PYPY,
 )
 from pandas.compat.numpy import (
     is_numpy_dev,
@@ -33,6 +33,12 @@
     pa_version_under9p0,
 )
 
+IS64 = IS64
+PY39 = PY39
+PY310 = PY310
+PY311 = PY311
+PYPY = PYPY
+
 
 def set_function_name(f: F, name: str, cls) -> F:
     """

From 092e726594384b58cc3ddeed6d9ace43d9a726f2 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Thu, 20 Oct 2022 12:50:34 -0700
Subject: [PATCH 38/41] Update changelog entry    [skip ci]

---
 doc/source/whatsnew/v2.0.0.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/source/whatsnew/v2.0.0.rst b/doc/source/whatsnew/v2.0.0.rst
index 6d145004e380b..a3dd79546d439 100644
--- a/doc/source/whatsnew/v2.0.0.rst
+++ b/doc/source/whatsnew/v2.0.0.rst
@@ -170,7 +170,7 @@ Performance improvements
 - Performance improvement in :func:`merge` and :meth:`DataFrame.join` when joining on a sorted :class:`MultiIndex` (:issue:`48504`)
 - Performance improvement in :meth:`DataFrame.loc` and :meth:`Series.loc` for tuple-based indexing of a :class:`MultiIndex` (:issue:`48384`)
 - Performance improvement for :meth:`MultiIndex.unique` (:issue:`48335`)
-- Performance use out-of-band pickling with BZ2 & LZMA files (:issue:`49068`)
+- Minimize memory usage when writing BZ2 & LZMA files by using out-of-band pickling (:issue:`49068`)
 - Performance improvement for :class:`~arrays.StringArray` constructor passing a numpy array with type ``np.str_`` (:issue:`49109`)
 - Performance improvement in :meth:`~arrays.ArrowExtensionArray.factorize` (:issue:`49177`)
 - Performance improvement for :func:`concat` with extension array backed indexes (:issue:`49128`)

From e49ba4f69e9669255787e3d4b3de5f3bb10ae2b3 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Thu, 20 Oct 2022 12:55:38 -0700
Subject: [PATCH 39/41] Add constants to `__all__`

---
 pandas/compat/__init__.py   | 11 +++++------
 pandas/compat/_constants.py |  9 +++++++++
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/pandas/compat/__init__.py b/pandas/compat/__init__.py
index 83a75ff4a6d67..f097b0c1ae630 100644
--- a/pandas/compat/__init__.py
+++ b/pandas/compat/__init__.py
@@ -33,12 +33,6 @@
     pa_version_under9p0,
 )
 
-IS64 = IS64
-PY39 = PY39
-PY310 = PY310
-PY311 = PY311
-PYPY = PYPY
-
 
 def set_function_name(f: F, name: str, cls) -> F:
     """
@@ -155,4 +149,9 @@ def get_lzma_file() -> type[pandas.compat._compressors.LZMAFile]:
     "pa_version_under7p0",
     "pa_version_under8p0",
     "pa_version_under9p0",
+    "IS64",
+    "PY39",
+    "PY310",
+    "PY311",
+    "PYPY",
 ]
diff --git a/pandas/compat/_constants.py b/pandas/compat/_constants.py
index cad5b8fc9b861..75d99f5ae51fb 100644
--- a/pandas/compat/_constants.py
+++ b/pandas/compat/_constants.py
@@ -16,3 +16,12 @@
 PY310 = sys.version_info >= (3, 10)
 PY311 = sys.version_info >= (3, 11)
 PYPY = platform.python_implementation() == "PyPy"
+
+
+__all__ = [
+    "IS64",
+    "PY39",
+    "PY310",
+    "PY311",
+    "PYPY",
+]

From 453b4e3bcb85370bb82c24175c2c6d8a682614b1 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Thu, 20 Oct 2022 20:46:45 -0700
Subject: [PATCH 40/41] Update changelog entry    [ci skip]

---
 doc/source/whatsnew/v2.0.0.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/source/whatsnew/v2.0.0.rst b/doc/source/whatsnew/v2.0.0.rst
index 3a70acf5c3eab..e6b5bc62af62a 100644
--- a/doc/source/whatsnew/v2.0.0.rst
+++ b/doc/source/whatsnew/v2.0.0.rst
@@ -185,7 +185,7 @@ Performance improvements
 - Performance improvement in :func:`merge` and :meth:`DataFrame.join` when joining on a sorted :class:`MultiIndex` (:issue:`48504`)
 - Performance improvement in :meth:`DataFrame.loc` and :meth:`Series.loc` for tuple-based indexing of a :class:`MultiIndex` (:issue:`48384`)
 - Performance improvement for :meth:`MultiIndex.unique` (:issue:`48335`)
-- Minimize memory usage when writing BZ2 & LZMA files by using out-of-band pickling (:issue:`49068`)
+- Reduce memory usage of DataFrame/Series `to_pickle` when using BZ2 or LZMA (:issue:`49068`)
 - Performance improvement for :class:`~arrays.StringArray` constructor passing a numpy array with type ``np.str_`` (:issue:`49109`)
 - Performance improvement in :meth:`~arrays.ArrowExtensionArray.factorize` (:issue:`49177`)
 - Performance improvement for :func:`concat` with extension array backed indexes (:issue:`49128`)

From 30124dda4a582fc20adea9dc53d3fa65d1edc8d6 Mon Sep 17 00:00:00 2001
From: jakirkham <jakirkham@gmail.com>
Date: Fri, 21 Oct 2022 08:22:50 -0700
Subject: [PATCH 41/41] Use Sphinx method annotation

---
 doc/source/whatsnew/v2.0.0.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/source/whatsnew/v2.0.0.rst b/doc/source/whatsnew/v2.0.0.rst
index e6b5bc62af62a..4475c58880fa1 100644
--- a/doc/source/whatsnew/v2.0.0.rst
+++ b/doc/source/whatsnew/v2.0.0.rst
@@ -185,7 +185,7 @@ Performance improvements
 - Performance improvement in :func:`merge` and :meth:`DataFrame.join` when joining on a sorted :class:`MultiIndex` (:issue:`48504`)
 - Performance improvement in :meth:`DataFrame.loc` and :meth:`Series.loc` for tuple-based indexing of a :class:`MultiIndex` (:issue:`48384`)
 - Performance improvement for :meth:`MultiIndex.unique` (:issue:`48335`)
-- Reduce memory usage of DataFrame/Series `to_pickle` when using BZ2 or LZMA (:issue:`49068`)
+- Reduce memory usage of :meth:`DataFrame.to_pickle`/:meth:`Series.to_pickle` when using BZ2 or LZMA (:issue:`49068`)
 - Performance improvement for :class:`~arrays.StringArray` constructor passing a numpy array with type ``np.str_`` (:issue:`49109`)
 - Performance improvement in :meth:`~arrays.ArrowExtensionArray.factorize` (:issue:`49177`)
 - Performance improvement for :func:`concat` with extension array backed indexes (:issue:`49128`)