What's New In Python 3.10
*************************

編集者:
   Pablo Galindo Salgado

この記事では Python 3.9 と比較した Python 3.10 の新機能を解説します。
Python 3.10 は2021年10月4日にリリースされました。全詳細については 変更
履歴 をご覧ください。


概要 -- リリースハイライト
==========================

新たな文法機能:

* **PEP 634**、構造的パターンマッチ: 仕様

* **PEP 635**、構造的パターンマッチ: モチベーションと原理

* **PEP 636**、構造的パターンマッチ: チュートリアル

* bpo-12782、カッコ内のコンテキストマネージャーが正式にサポート

標準ライブラリの新機能:

* **PEP 618**、zipに長さチェックのオプション引数が追加

インタプリタの改善:

* **PEP 626**, デバッグおよびその他のツール用の正確な行番号。

新しい型ヒントの機能:

* **PEP 604**, Unionタイプの X | Y 形式での表示

* **PEP 612**, パラメータ指定変数

* **PEP 613**, 明示的型エイリアス

* **PEP 647**, ユーザ定義型ガード

重要な非推奨化、削除または制限:

* **PEP 644**, OpenSSL 1.1.1 以降の必須化

* **PEP 632**, distutilsモジュールが非推奨に

* **PEP 623**, PyUnicodeObject の wstr メンバーの非推奨・削除への準備

* **PEP 624**, Py_UNICODE エンコーダAPIの削除

* **PEP 597**, 任意のEncodingWarningを追加


新しい機能
==========


カッコ内のコンテキストマネージャー
----------------------------------

コンテキストマネージャーを複数行で継続して記述する場合に、カッコで囲む
ことができるようになりました。複数行でたくさんのコンテキストマネージャ
ーを記述するときに、従来のimport文と同じようにフォーマットできます。た
とえば、以下のすべての例は有効です:

   with (CtxManager() as example):
       ...

   with (
       CtxManager1(),
       CtxManager2()
   ):
       ...

   with (CtxManager1() as example,
         CtxManager2()):
       ...

   with (CtxManager1(),
         CtxManager2() as example):
       ...

   with (
       CtxManager1() as example1,
       CtxManager2() as example2
   ):
       ...

カッコに囲まれたグループの最後の要素に対する、末尾のカンマも指定可能で
す。

   with (
       CtxManager1() as example1,
       CtxManager2() as example2,
       CtxManager3() as example3,
   ):
       ...

この新しい構文は、新パーサーによるLL(1)以外の能力を使用しています。詳
細は **PEP 617** を参照してください。

(Guido van Rossum、Pablo Galindo、Lysandros Nikolaou の貢献による
bpo-12782、bpo-40334)


エラーメッセージの改善
----------------------


SyntaxErrors
~~~~~~~~~~~~

閉じられていない括弧やブラケットを含むコードを解析する際、インタープリ
タはこれまでのように *SyntaxError: unexpected EOF while parsing* を表
示したり、誤った位置を指したりするのではなく、未閉鎖の括弧やブラケット
の位置を示すようになりました。たとえば、次のコードを考えてみましょう（
未閉鎖の '{' に注目してください）:

   expected = {9: 1, 18: 2, 19: 2, 27: 3, 28: 3, 29: 3, 36: 4, 37: 4,
               38: 4, 39: 4, 45: 5, 46: 5, 47: 5, 48: 5, 49: 5, 54: 6,
   some_other_code = foo()

以前のバージョンのインタープリタは、構文エラーの位置として混乱する場所
を報告していました:

   File "example.py", line 3
       some_other_code = foo()
                       ^
   SyntaxError: invalid syntax

しかしPython 3.10ではより有益なエラーが出力されます:

   File "example.py", line 1
       expected = {9: 1, 18: 2, 19: 2, 27: 3, 28: 3, 29: 3, 36: 4, 37: 4,
                  ^
   SyntaxError: '{' was never closed

同様に、閉じられていない文字列リテラル（シングルクォートおよびトリプル
クォート）に関するエラーも、これまでのように EOF/EOL を報告するのでは
なく、文字列の開始位置を指すようになりました。

これらの改善は PyPy インタプリタのこれまでの取組から着想を得ました。

(Pablo Galindoの貢献による bpo-42864、Batuhan Taskayaの貢献による
bpo-40176)

インタープリタによって発生する:exc:*SyntaxError* 例外は、これまで問題
が検出された箇所のみを強調表示していましたが、今後は構文エラーを構成す
る式全体の範囲を強調表示するようになりました。このため、（ Python 3.10
以前で）次のように表示されていたものが、

   >>> foo(x, z for z in range(10), t, w)
     File "<stdin>", line 1
       foo(x, z for z in range(10), t, w)
              ^
   SyntaxError: Generator expression must be parenthesized

Python 3.10 では例外は次のように表示されるようになります:

   >>> foo(x, z for z in range(10), t, w)
     File "<stdin>", line 1
       foo(x, z for z in range(10), t, w)
              ^^^^^^^^^^^^^^^^^^^^
   SyntaxError: Generator expression must be parenthesized

この改善は Pablo Galindo の貢献で実現しました bpo-43914。

多くの新しい種類の:exc:*SyntaxError* 例外に対して、より具体的でわかり
やすいエラーメッセージが追加されました。その中でも特に注目すべきものを
以下に示します。

* ブロックの前の ":" が存在しない:

     >>> if rocket.position > event_horizon
       File "<stdin>", line 1
         if rocket.position > event_horizon
                                           ^
     SyntaxError: expected ':'

  (Pablo Galindo の貢献による bpo-42997)

* 内包表記のターゲットにカッコのないタプルを使用:

     >>> {x,y for x,y in zip('abcd', '1234')}
       File "<stdin>", line 1
         {x,y for x,y in zip('abcd', '1234')}
          ^
     SyntaxError: did you forget parentheses around the comprehension target?

  (Pablo Galindo の貢献による bpo-43017)

* コレクションリテラルや式の間のカンマが存在しない:

     >>> items = {
     ... x: 1,
     ... y: 2
     ... z: 3,
       File "<stdin>", line 3
         y: 2
            ^
     SyntaxError: invalid syntax. Perhaps you forgot a comma?

  (Pablo Galindo の貢献による bpo-43822)

* 複数の例外の型をカッコで囲んでいない:

     >>> try:
     ...     build_dyson_sphere()
     ... except NotEnoughScienceError, NotEnoughResourcesError:
       File "<stdin>", line 3
         except NotEnoughScienceError, NotEnoughResourcesError:
                ^
     SyntaxError: multiple exception types must be parenthesized

  (Pablo Galindo の貢献による bpo-43149)

* 辞書のリテラルで ":" と値が存在しない:

     >>> values = {
     ... x: 1,
     ... y: 2,
     ... z:
     ... }
       File "<stdin>", line 4
         z:
          ^
     SyntaxError: expression expected after dictionary key and ':'

     >>> values = {x:1, y:2, z w:3}
       File "<stdin>", line 1
         values = {x:1, y:2, z w:3}
                             ^
     SyntaxError: ':' expected after dictionary key

  (Pablo Galindo の貢献による bpo-43823)

* "try" ブロックに "except" または "finally" ブロックが存在しない:

     >>> try:
     ...     x = 2
     ... something = 3
       File "<stdin>", line 3
         something  = 3
         ^^^^^^^^^
     SyntaxError: expected 'except' or 'finally' block

  (Pablo Galindo の貢献による bpo-44305)

* 比較で "==" の代わりに "=" を使用している:

     >>> if rocket.position = event_horizon:
       File "<stdin>", line 1
         if rocket.position = event_horizon:
                            ^
     SyntaxError: cannot assign to attribute here. Maybe you meant '==' instead of '='?

  (Pablo Galindo の貢献による bpo-43797)

* f-stringで "*" を使用している:

     >>> f"Black holes {*all_black_holes} and revelations"
       File "<stdin>", line 1
         (*all_black_holes)
          ^
     SyntaxError: f-string: cannot use starred expression here

  (Pablo Galindo の貢献による bpo-41064)


IndentationErrors
~~~~~~~~~~~~~~~~~

多くの:exc:*IndentationError* 例外において、どの種類のブロックでインデ
ントが期待されていたのか、その文の位置に関する情報が追加されるようにな
りました。

   >>> def foo():
   ...    if lel:
   ...    x = 2
     File "<stdin>", line 3
       x = 2
       ^
   IndentationError: expected an indented block after 'if' statement in line 2


AttributeErrors
~~~~~~~~~~~~~~~

When printing "AttributeError", "PyErr_Display()" will offer
suggestions of similar attribute names in the object that the
exception was raised from:

   >>> collections.namedtoplo
   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
   AttributeError: module 'collections' has no attribute 'namedtoplo'. Did you mean: namedtuple?

(Pablo Galindo の貢献による bpo-38530)

警告:

  Notice this won't work if "PyErr_Display()" is not called to display
  the error which can happen if some other custom error display
  function is used. This is a common scenario in some REPLs like
  IPython.


NameErrors
~~~~~~~~~~

When printing "NameError" raised by the interpreter, "PyErr_Display()"
will offer suggestions of similar variable names in the function that
the exception was raised from:

   >>> schwarzschild_black_hole = None
   >>> schwarschild_black_hole
   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
   NameError: name 'schwarschild_black_hole' is not defined. Did you mean: schwarzschild_black_hole?

(Pablo Galindo の貢献による bpo-38530)

警告:

  Notice this won't work if "PyErr_Display()" is not called to display
  the error, which can happen if some other custom error display
  function is used. This is a common scenario in some REPLs like
  IPython.


PEP 626: デバッグおよびその他のツール用の正確な行番号。
-------------------------------------------------------

PEP 626 brings more precise and reliable line numbers for debugging,
profiling and coverage tools. Tracing events, with the correct line
number, are generated for all lines of code executed and only for
lines of code that are executed.

The "f_lineno" attribute of frame objects will always contain the
expected line number.

The "co_lnotab" attribute of code objects is deprecated and will be
removed in 3.12. Code that needs to convert from offset to line number
should use the new "co_lines()" method instead.


PEP 634: 構造的パターンマッチ
-----------------------------

Structural pattern matching has been added in the form of a *match
statement* and *case statements* of patterns with associated actions.
Patterns consist of sequences, mappings, primitive data types as well
as class instances. Pattern matching enables programs to extract
information from complex data types, branch on the structure of data,
and apply specific actions based on different forms of data.


構文と演算
~~~~~~~~~~

パターンマッチングの一般的な構文は次のとおりです:

   match subject:
       case <pattern_1>:
           <action_1>
       case <pattern_2>:
           <action_2>
       case <pattern_3>:
           <action_3>
       case _:
           <action_wildcard>

match 文は式を取り、その値を 1 つ以上の case ブロックで指定されたパタ
ーンと順に比較します。具体的には、パターンマッチングは次の手順で動作し
ます:

1. 型と構造を持つデータ（"subject"）を使用する

2. "match" 文内で "subject" を評価する

3. "case" 文の各パターンと上から順に比較し、一致が確認されるまで進める

4. 一致が確認されたパターンに関連付けられた処理を実行する

5. 完全一致するパターンがない場合、最後にワイルドカード "_" が指定され
   ていれば、それが一致ケースとして使用されます。完全一致もワイルドカ
   ードも存在しない場合、 match ブロック全体は何も実行されません（no-
   op となります）。


宣言的なアプローチ
~~~~~~~~~~~~~~~~~~

読者の中には、C、Java、JavaScript（およびその他多くの言語）における
switch 文を通じて、対象（データオブジェクト）をリテラル（パターン）と
照合する単純な例として、パターンマッチングに馴染みがある方もいるでしょ
う。多くの場合、 switch 文はオブジェクトや式を、リテラルを含む複数の
case 文と比較するために使用されます。

より強力なパターンマッチングの例は、Scala や Elixir のような言語で見ら
れます。構造的パターンマッチングでは、アプローチは「宣言的」であり、デ
ータが一致するための条件（パターン）を明示的に記述します。

これに対して、「命令的」なアプローチでは、入れ子になった if 文を用いて
構造的パターンマッチングと同様の処理を実現することも可能ですが、「宣言
的」な方法ほど明確ではありません。宣言的アプローチでは、一致のために満
たすべき条件を明示的なパターンとして記述するため、より読みやすくなりま
す。構造的パターンマッチングは、最も単純な形では case 文で変数とリテラ
ルを比較するものとして使用できますが、 Python における真の価値は、対象
の型や構造を扱える点にあります。


単純パターン: リテラルとのマッチ
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

最も基本的な形のパターンマッチングの例を見てみましょう。ここでは、値（
＝対象、subject）が複数のリテラル、すなわちパターンと照合されます。以
下の例では、"status" が match 文の対象です。 各 case 文のパターンは、
リクエストのステータスコードを表すリテラルです。一致が見つかると、その
case に対応する処理が実行されます。

   def http_error(status):
       match status:
           case 400:
               return "Bad request"
           case 404:
               return "Not found"
           case 418:
               return "I'm a teapot"
           case _:
               return "Something's wrong with the internet"

上記の関数に "status" として 418 が渡された場合は、 "I'm a teapot" が
返されます。一方、 500 が渡された場合には、ワイルドカードとして機能す
る "_" を使用した case 文が一致し、 "Something's wrong with the
internet" が返されます。ここで、最後のブロックに注目してください。変数
名 "_" はワイルドカードとして機能し、対象と必ず一致することを保証しま
す。なお、 "_" の使用は任意です。

複数のリテラルを "|" ("or")を使用して組み合わせて1つのパターンにできま
す。

   case 401 | 403 | 404:
       return "Not allowed"


ワイルドカードがないときの振る舞い
""""""""""""""""""""""""""""""""""

上記の例から最後の case ブロックを削除すると、次のようになります:

   def http_error(status):
       match status:
           case 400:
               return "Bad request"
           case 404:
               return "Not found"
           case 418:
               return "I'm a teapot"

case 文で "_" を使用しない場合、一致するパターンが存在しない可能性があ
ります。一致するパターンがない場合、その処理は何も実行されずスキップさ
れます。たとえば、 "status" に 500 が渡された場合、この例では何も起こ
りません。


リテラルと変数を組み合わせたパターン
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

パターンはアンパック代入のように記述することで、変数をバインドするため
に使用することもできます。次の例では、データポイントを展開して、その x
座標と y 座標を取得しています:

   # point は (x, y) のタプル
   match point:
       case (0, 0):
           print("Origin")
       case (0, y):
           print(f"Y={y}")
       case (x, 0):
           print(f"X={x}")
       case (x, y):
           print(f"X={x}, Y={y}")
       case _:
           raise ValueError("Not a point")

最初のパターン "(0, 0)" は 2 つのリテラルから構成されており、上で示し
たリテラルパターン拡張と考えることができます。次の 2 つのパターンでは
、リテラルと変数が組み合わされており、変数は対象（"point"）から値を取
り出して変数にバインドします。4 番目のパターンは 2 つの値を同時に取得
しており、これはアンパック代入 "(x, y) = point" と概念的に似ています。


パターンとクラス
~~~~~~~~~~~~~~~~

データを構造化するためにクラスを使用している場合は、クラス名の後ろにコ
ンストラクタのように引数リストを指定することで、クラスをパターンとして
使用できます。このパターンでは、インスタンスの属性を変数にバインドする
ことが可能です:

   class Point:
       def __init__(self, x, y):
           self.x = x
           self.y = y

   def location(point):
       match point:
           case Point(x=0, y=0):
               print("原点")
           case Point(x=0, y=y):
               print(f"Y座標は {y} で点はY軸上にある")
           case Point(x=x, y=0):
               print(f"X座標は {x} で点はX軸上にある")
           case Point():
               print("点は平面上のそれ以外のどこかにある")
           case _:
               print("座標ではない")


位置パラメータを用いたパターン
""""""""""""""""""""""""""""""

いくつかの組み込みクラスでは位置引数が使用でき、属性の順番を提供します
(例: データクラス)。クラスの "__match_args__" 特殊属性でによって、パタ
ーンの中で属性の明確な位置を定義することもできます。("x", "y")が設定さ
れた場合、以下のすべてのパターンは等価です(すべて属性 "y" が "var" 変
数に関連づけられます):

   Point(1, var)
   Point(1, y=var)
   Point(x=1, y=var)
   Point(y=var, x=1)


ネストしたパターン
~~~~~~~~~~~~~~~~~~

パターンは任意に入れ子にすることができます。たとえば、データが複数のポ
イントを含む短いリストである場合、次のようにマッチさせることができます
:

   match points:
       case []:
           print("リストに座標がない")
       case [Point(0, 0)]:
           print("リスト中には原点が1つのみある")
       case [Point(x, y)]:
           print(f"リスト中に {x}, {y} の点が1つある")
       case [Point(0, y1), Point(0, y2)]:
           print(f"リスト中にY軸上の2つの点 {y1}、{y2} がある")
       case _:
           print("リスト中にそれ以外のデータが見つかった")


複雑なパターンとワイルドカード
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

ここまでの例では、最後の case 文で "_" を単独のワイルドカードとして使
用してきました。しかし、ワイルドカードはより複雑なパターン内でも使用で
きます。たとえば、 "('error', code, _)" のように使用することができます
。

   match test_variable:
       case ('warning', code, 40):
           print("警告を受け取った")
       case ('error', code, _):
           print(f"エラー {code} が発生した")

上記のケースでは、 "test_variable" は ('error', code, 100) と
('error', code, 800) にマッチします。


ガード
~~~~~~

パターンに "if" 節を追加できます。これは "ガード" と呼ばれます。ガード
がfalseの場合、"match" は次のcaseブロックの処理に移動します。ガードを
評価する前に値が取り出されることに注意してください:

   match point:
       case Point(x, y) if x == y:
           print(f"座標は対角線 Y=X 上の {x} の位置にある")
       case Point(x, y):
           print(f"座標の位置は対角線上ではない")


その他の主要な機能
~~~~~~~~~~~~~~~~~~

その他のいくつかの主要な機能:

* アンパック代入と同様に、タプルおよびリストのパターンはまったく同じ意
  味を持ち、任意のシーケンスにマッチします。技術的には、対象はシーケン
  スである必要があります。そのため、重要な例外として、パターンはイテレ
  ータにはマッチしません。また、よくある誤りを防ぐために、シーケンスパ
  ターンは文字列にもマッチしません。

* シーケンスパターンではワイルドカードをサポートしています。たとえば、
  "[x, y, *rest]" や "(x, y, *rest)" は、アンパック代入におけるワイル
  ドカードと同様に動作します。"*" の後の名前を "_" にすることもでき、
  "(x, y, *_)" は少なくとも 2 つの要素を持つシーケンスにマッチしますが
  、残りの要素は変数に束縛されません。

* マッピングパターン: "{"bandwidth": b, "latency": l}" では、辞書から
  ""bandwidth"" と ""latency"" の値を取得します。シーケンスパターンと
  は異なり、余分なキーは無視されます。また、ワイルドカード "**rest" も
  サポートされています。（ただし、"**_" は冗長になるため使用できません
  。）

* サブパターンでは "as" キーワードを使用して値を取り込みます:

     case (Point(x1, y1), Point(x2, y2) as p2): ...

  このように書くと x1、y1、x2、y2 は "as" 節を使わないときと同様に、さ
  らにp2に対象の2番目の要素全体がバインドされます。

* ほとんどのリテラルは同一性を比較します。しかし、シングルトンの
  "True"、"False"、"None" では識別値を比較します。

* 名前を付けた定数をパターンに使用できます。名前を付けた定数を、値を取
  り込む変数として解釈することを防ぐために、ドット付きの変数名にする必
  要があります。

     from enum import Enum
     class Color(Enum):
         RED = 0
         GREEN = 1
         BLUE = 2

     color = Color.GREEN
     match color:
         case Color.RED:
             print("I see red!")
         case Color.GREEN:
             print("Grass is green")
         case Color.BLUE:
             print("I'm feeling the blues :(")

完全な仕様については **PEP 634** を参照してください。モチベーションと
理論的根拠は **PEP 635** に、より詳細なチュートリアルは **PEP 636** に
あります。


Optional "EncodingWarning" and "encoding="locale"" option
---------------------------------------------------------

The default encoding of "TextIOWrapper" and "open()" is platform and
locale dependent. Since UTF-8 is used on most Unix platforms, omitting
"encoding" option when opening UTF-8 files (e.g. JSON, YAML, TOML,
Markdown) is a very common bug. For example:

   # BUG: "rb" mode or encoding="utf-8" should be used.
   with open("data.json") as f:
       data = json.load(f)

To find this type of bug, an optional "EncodingWarning" is added. It
is emitted when "sys.flags.warn_default_encoding" is true and locale-
specific default encoding is used.

"-X warn_default_encoding" option and "PYTHONWARNDEFAULTENCODING" are
added to enable the warning.

See Text Encoding for more information.


型ヒントに関連する新しい機能
============================

This section covers major changes affecting **PEP 484** type hints and
the "typing" module.


PEP 604: New Type Union Operator
--------------------------------

A new type union operator was introduced which enables the syntax "X |
Y". This provides a cleaner way of expressing 'either type X or type
Y' instead of using "typing.Union", especially in type hints.

In previous versions of Python, to apply a type hint for functions
accepting arguments of multiple types, "typing.Union" was used:

   def square(number: Union[int, float]) -> Union[int, float]:
       return number ** 2

Type hints can now be written in a more succinct manner:

   def square(number: int | float) -> int | float:
       return number ** 2

This new syntax is also accepted as the second argument to
"isinstance()" and "issubclass()":

   >>> isinstance(1, int | str)
   True

See Union 型 and **PEP 604** for more details.

(Contributed by Maggie Moss and Philippe Prados in bpo-41428, with
additions by Yurii Karabas and Serhiy Storchaka in bpo-44490.)


PEP 612: Parameter Specification Variables
------------------------------------------

Two new options to improve the information provided to static type
checkers for **PEP 484**'s "Callable" have been added to the "typing"
module.

The first is the parameter specification variable.  They are used to
forward the parameter types of one callable to another callable -- a
pattern commonly found in higher order functions and decorators.
Examples of usage can be found in "typing.ParamSpec". Previously,
there was no easy way to type annotate dependency of parameter types
in such a precise manner.

The second option is the new "Concatenate" operator. It's used in
conjunction with parameter specification variables to type annotate a
higher order callable which adds or removes parameters of another
callable.  Examples of usage can be found in "typing.Concatenate".

See "typing.Callable", "typing.ParamSpec", "typing.Concatenate",
"typing.ParamSpecArgs", "typing.ParamSpecKwargs", and **PEP 612** for
more details.

(Contributed by Ken Jin in bpo-41559, with minor enhancements by Jelle
Zijlstra in bpo-43783.  PEP written by Mark Mendoza.)


PEP 613: TypeAlias
------------------

**PEP 484** introduced the concept of type aliases, only requiring
them to be top-level unannotated assignments. This simplicity
sometimes made it difficult for type checkers to distinguish between
type aliases and ordinary assignments, especially when forward
references or invalid types were involved. Compare:

   StrCache = 'Cache[str]'  # a type alias
   LOG_PREFIX = 'LOG[DEBUG]'  # a module constant

Now the "typing" module has a special value "TypeAlias" which lets you
declare type aliases more explicitly:

   StrCache: TypeAlias = 'Cache[str]'  # a type alias
   LOG_PREFIX = 'LOG[DEBUG]'  # a module constant

より詳しくは、 **PEP 613** をご覧ください。

(Contributed by Mikhail Golubev in bpo-41923.)


PEP 647: User-Defined Type Guards
---------------------------------

"TypeGuard" has been added to the "typing" module to annotate type
guard functions and improve information provided to static type
checkers during type narrowing.  For more information, please see
"TypeGuard"'s documentation, and **PEP 647**.

(Contributed by Ken Jin and Guido van Rossum in bpo-43766. PEP written
by Eric Traut.)


その他の言語変更
================

* The "int" type has a new method "int.bit_count()", returning the
  number of ones in the binary expansion of a given integer, also
  known as the population count. (Contributed by Niklas Fiekas in
  bpo-29882.)

* The views returned by "dict.keys()", "dict.values()" and
  "dict.items()" now all have a "mapping" attribute that gives a
  "types.MappingProxyType" object wrapping the original dictionary.
  (Contributed by Dennis Sweeney in bpo-40890.)

* **PEP 618**: The "zip()" function now has an optional "strict" flag,
  used to require that all the iterables have an equal length.

* Builtin and extension functions that take integer arguments no
  longer accept "Decimal"s, "Fraction"s and other objects that can be
  converted to integers only with a loss (e.g. that have the
  "__int__()" method but do not have the "__index__()" method).
  (Contributed by Serhiy Storchaka in bpo-37999.)

* If "object.__ipow__()" returns "NotImplemented", the operator will
  correctly fall back to "object.__pow__()" and "object.__rpow__()" as
  expected. (Contributed by Alex Shkop in bpo-38302.)

* Assignment expressions can now be used unparenthesized within set
  literals and set comprehensions, as well as in sequence indexes (but
  not slices).

* Functions have a new "__builtins__" attribute which is used to look
  for builtin symbols when a function is executed, instead of looking
  into "__globals__['__builtins__']". The attribute is initialized
  from "__globals__["__builtins__"]" if it exists, else from the
  current builtins. (Contributed by Mark Shannon in bpo-42990.)

* Two new builtin functions -- "aiter()" and "anext()" have been added
  to provide asynchronous counterparts to "iter()" and "next()",
  respectively. (Contributed by Joshua Bronson, Daniel Pope, and
  Justin Wang in bpo-31861.)

* Static methods ("@staticmethod") and class methods ("@classmethod")
  now inherit the method attributes ("__module__", "__name__",
  "__qualname__", "__doc__", "__annotations__") and have a new
  "__wrapped__" attribute. Moreover, static methods are now callable
  as regular functions. (Contributed by Victor Stinner in bpo-43682.)

* Annotations for complex targets (everything beside "simple name"
  targets defined by **PEP 526**) no longer cause any runtime effects
  with "from __future__ import annotations". (Contributed by Batuhan
  Taskaya in bpo-42737.)

* Class and module objects now lazy-create empty annotations dicts on
  demand. The annotations dicts are stored in the object’s "__dict__"
  for backwards compatibility.  This improves the best practices for
  working with "__annotations__"; for more information, please see ア
  ノテーションのベストプラクティス. (Contributed by Larry Hastings in
  bpo-43901.)

* Annotations consist of "yield", "yield from", "await" or named
  expressions are now forbidden under "from __future__ import
  annotations" due to their side effects. (Contributed by Batuhan
  Taskaya in bpo-42725.)

* Usage of unbound variables, "super()" and other expressions that
  might alter the processing of symbol table as annotations are now
  rendered effectless under "from __future__ import annotations".
  (Contributed by Batuhan Taskaya in bpo-42725.)

* Hashes of NaN values of both "float" type and "decimal.Decimal" type
  now depend on object identity. Formerly, they always hashed to "0"
  even though NaN values are not equal to one another. This caused
  potentially quadratic runtime behavior due to excessive hash
  collisions when creating dictionaries and sets containing multiple
  NaNs. (Contributed by Raymond Hettinger in bpo-43475.)

* A "SyntaxError" (instead of a "NameError") will be raised when
  deleting the "__debug__" constant.  (Contributed by Donghee Na in
  bpo-45000.)

* "SyntaxError" exceptions now have "end_lineno" and "end_offset"
  attributes.  They will be "None" if not determined. (Contributed by
  Pablo Galindo in bpo-43914.)


新たなモジュール
================

* None.


改良されたモジュール
====================


asyncio
-------

Add missing "connect_accepted_socket()" method. (Contributed by Alex
Grönholm in bpo-41332.)


argparse
--------

Misleading phrase "optional arguments" was replaced with "options" in
argparse help. Some tests might require adaptation if they rely on
exact output match. (Contributed by Raymond Hettinger in bpo-9694.)


array
-----

The "index()" method of "array.array" now has optional *start* and
*stop* parameters. (Contributed by Anders Lorentsen and Zackery Spytz
in bpo-31956.)


asynchat, asyncore, smtpd
-------------------------

These modules have been marked as deprecated in their module
documentation since Python 3.6.  An import-time "DeprecationWarning"
has now been added to all three of these modules.


base64
------

Add "base64.b32hexencode()" and "base64.b32hexdecode()" to support the
Base32 Encoding with Extended Hex Alphabet.


bdb
---

Add "clearBreakpoints()" to reset all set breakpoints. (Contributed by
Irit Katriel in bpo-24160.)


bisect
------

Added the possibility of providing a *key* function to the APIs in the
"bisect" module. (Contributed by Raymond Hettinger in bpo-4356.)


codecs
------

Add a "codecs.unregister()" function to unregister a codec search
function. (Contributed by Hai Shi in bpo-41842.)


collections.abc
---------------

The "__args__" of the parameterized generic for
"collections.abc.Callable" are now consistent with "typing.Callable".
"collections.abc.Callable" generic now flattens type parameters,
similar to what "typing.Callable" currently does.  This means that
"collections.abc.Callable[[int, str], str]" will have "__args__" of
"(int, str, str)"; previously this was "([int, str], str)".  To allow
this change, "types.GenericAlias" can now be subclassed, and a
subclass will be returned when subscripting the
"collections.abc.Callable" type.  Note that a "TypeError" may be
raised for invalid forms of parameterizing "collections.abc.Callable"
which may have passed silently in Python 3.9. (Contributed by Ken Jin
in bpo-42195.)


contextlib
----------

Add a "contextlib.aclosing()" context manager to safely close async
generators and objects representing asynchronously released resources.
(Contributed by Joongi Kim and John Belmonte in bpo-41229.)

Add asynchronous context manager support to
"contextlib.nullcontext()". (Contributed by Tom Gringauz in
bpo-41543.)

Add "AsyncContextDecorator", for supporting usage of async context
managers as decorators.


curses
------

The extended color functions added in ncurses 6.1 will be used
transparently by "curses.color_content()", "curses.init_color()",
"curses.init_pair()", and "curses.pair_content()". A new function,
"curses.has_extended_color_support()", indicates whether extended
color support is provided by the underlying ncurses library.
(Contributed by Jeffrey Kintscher and Hans Petter Jansson in
bpo-36982.)

The "BUTTON5_*" constants are now exposed in the "curses" module if
they are provided by the underlying curses library. (Contributed by
Zackery Spytz in bpo-39273.)


データクラス
------------


__slots__
~~~~~~~~~

Added "slots" parameter in "@dataclasses.dataclass" decorator.
(Contributed by Yurii Karabas in bpo-42269)


Keyword-only fields
~~~~~~~~~~~~~~~~~~~

dataclasses now supports fields that are keyword-only in the generated
__init__ method.  There are a number of ways of specifying keyword-
only fields.

You can say that every field is keyword-only:

   from dataclasses import dataclass

   @dataclass(kw_only=True)
   class Birthday:
       name: str
       birthday: datetime.date

Both "name" and "birthday" are keyword-only parameters to the
generated __init__ method.

You can specify keyword-only on a per-field basis:

   from dataclasses import dataclass, field

   @dataclass
   class Birthday:
       name: str
       birthday: datetime.date = field(kw_only=True)

Here only "birthday" is keyword-only.  If you set "kw_only" on
individual fields, be aware that there are rules about re-ordering
fields due to keyword-only fields needing to follow non-keyword-only
fields.  See the full dataclasses documentation for details.

You can also specify that all fields following a KW_ONLY marker are
keyword-only.  This will probably be the most common usage:

   from dataclasses import dataclass, KW_ONLY

   @dataclass
   class Point:
       x: float
       y: float
       _: KW_ONLY
       z: float = 0.0
       t: float = 0.0

Here, "z" and "t" are keyword-only parameters, while "x" and "y" are
not. (Contributed by Eric V. Smith in bpo-43532.)


distutils
---------

The entire "distutils" package is deprecated, to be removed in Python
3.12. Its functionality for specifying package builds has already been
completely replaced by third-party packages "setuptools" and
"packaging", and most other commonly used APIs are available elsewhere
in the standard library (such as "platform", "shutil", "subprocess" or
"sysconfig"). There are no plans to migrate any other functionality
from "distutils", and applications that are using other functions
should plan to make private copies of the code. Refer to **PEP 632**
for discussion.

The "bdist_wininst" command deprecated in Python 3.8 has been removed.
The "bdist_wheel" command is now recommended to distribute binary
packages on Windows. (Contributed by Victor Stinner in bpo-42802.)


doctest
-------

When a module does not define "__loader__", fall back to
"__spec__.loader". (Contributed by Brett Cannon in bpo-42133.)


エンコーディング
----------------

"encodings.normalize_encoding()" now ignores non-ASCII characters.
(Contributed by Hai Shi in bpo-39337.)


enum
----

"Enum" "__repr__()" now returns "enum_name.member_name" and
"__str__()" now returns "member_name".  Stdlib enums available as
module constants have a "repr()" of "module_name.member_name".
(Contributed by Ethan Furman in bpo-40066.)

Add "enum.StrEnum" for enums where all members are strings.
(Contributed by Ethan Furman in bpo-41816.)


fileinput
---------

Add *encoding* and *errors* parameters in "fileinput.input()" and
"fileinput.FileInput". (Contributed by Inada Naoki in bpo-43712.)

"fileinput.hook_compressed()" now returns "TextIOWrapper" object when
*mode* is "r" and file is compressed, like uncompressed files.
(Contributed by Inada Naoki in bpo-5758.)


faulthandler
------------

The "faulthandler" module now detects if a fatal error occurs during a
garbage collector collection. (Contributed by Victor Stinner in
bpo-44466.)


gc
--

Add audit hooks for "gc.get_objects()", "gc.get_referrers()" and
"gc.get_referents()". (Contributed by Pablo Galindo in bpo-43439.)


glob
----

Add the *root_dir* and *dir_fd* parameters in "glob()" and "iglob()"
which allow to specify the root directory for searching. (Contributed
by Serhiy Storchaka in bpo-38144.)


hashlib
-------

The hashlib module requires OpenSSL 1.1.1 or newer. (Contributed by
Christian Heimes in **PEP 644** and bpo-43669.)

The hashlib module has preliminary support for OpenSSL 3.0.0.
(Contributed by Christian Heimes in bpo-38820 and other issues.)

The pure-Python fallback of "pbkdf2_hmac()" is deprecated. In the
future PBKDF2-HMAC will only be available when Python has been built
with OpenSSL support. (Contributed by Christian Heimes in bpo-43880.)


hmac
----

The hmac module now uses OpenSSL's HMAC implementation internally.
(Contributed by Christian Heimes in bpo-40645.)


IDLE と idelelib
----------------

Make IDLE invoke "sys.excepthook()" (when started without '-n'). User
hooks were previously ignored.  (Contributed by Ken Hilton in
bpo-43008.)

Rearrange the settings dialog.  Split the General tab into Windows and
Shell/Ed tabs.  Move help sources, which extend the Help menu, to the
Extensions tab.  Make space for new options and shorten the dialog.
The latter makes the dialog better fit small screens.  (Contributed by
Terry Jan Reedy in bpo-40468.)  Move the indent space setting from the
Font tab to the new Windows tab.  (Contributed by Mark Roseman and
Terry Jan Reedy in bpo-33962.)

The changes above were backported to a 3.9 maintenance release.

Add a Shell sidebar.  Move the primary prompt ('>>>') to the sidebar.
Add secondary prompts ('...') to the sidebar.  Left click and optional
drag selects one or more lines of text, as with the editor line number
sidebar.  Right click after selecting text lines displays a context
menu with 'copy with prompts'.  This zips together prompts from the
sidebar with lines from the selected text.  This option also appears
on the context menu for the text.  (Contributed by Tal Einat in
bpo-37903.)

Use spaces instead of tabs to indent interactive code.  This makes
interactive code entries 'look right'.  Making this feasible was a
major motivation for adding the shell sidebar.  (Contributed by Terry
Jan Reedy in bpo-37892.)

Highlight the new soft keywords "match", "case", and "_" in pattern-
matching statements. However, this highlighting is not perfect and
will be incorrect in some rare cases, including some "_"-s in "case"
patterns.  (Contributed by Tal Einat in bpo-44010.)

New in 3.10 maintenance releases.

Apply syntax highlighting to ".pyi" files. (Contributed by Alex
Waygood and Terry Jan Reedy in bpo-45447.)

Include prompts when saving Shell with inputs and outputs.
(Contributed by Terry Jan Reedy in gh-95191.)


importlib.metadata
------------------

Feature parity with "importlib_metadata" 4.6 (history).

importlib.metadata entry points now provide a nicer experience for
selecting entry points by group and name through a new
importlib.metadata.EntryPoints class. See the Compatibility Note in
the docs for more info on the deprecation and usage.

Added importlib.metadata.packages_distributions() for resolving top-
level Python modules and packages to their
importlib.metadata.Distribution.


inspect
-------

When a module does not define "__loader__", fall back to
"__spec__.loader". (Contributed by Brett Cannon in bpo-42133.)

Add "inspect.get_annotations()", which safely computes the annotations
defined on an object. It works around the quirks of accessing the
annotations on various types of objects, and makes very few
assumptions about the object it examines. "inspect.get_annotations()"
can also correctly un-stringize stringized annotations.
"inspect.get_annotations()" is now considered best practice for
accessing the annotations dict defined on any Python object; for more
information on best practices for working with annotations, please see
アノテーションのベストプラクティス. Relatedly, "inspect.signature()",
"inspect.Signature.from_callable()", and
"inspect.Signature.from_function()" now call
"inspect.get_annotations()" to retrieve annotations. This means
"inspect.signature()" and "inspect.Signature.from_callable()" can also
now un-stringize stringized annotations. (Contributed by Larry
Hastings in bpo-43817.)


itertools
---------

Add "itertools.pairwise()". (Contributed by Raymond Hettinger in
bpo-38200.)


linecache
---------

When a module does not define "__loader__", fall back to
"__spec__.loader". (Contributed by Brett Cannon in bpo-42133.)


os
--

Add "os.cpu_count()" support for VxWorks RTOS. (Contributed by Peixing
Xin in bpo-41440.)

Add a new function "os.eventfd()" and related helpers to wrap the
"eventfd2" syscall on Linux. (Contributed by Christian Heimes in
bpo-41001.)

Add "os.splice()" that allows to move data between two file
descriptors without copying between kernel address space and user
address space, where one of the file descriptors must refer to a pipe.
(Contributed by Pablo Galindo in bpo-41625.)

Add "O_EVTONLY", "O_FSYNC", "O_SYMLINK" and "O_NOFOLLOW_ANY" for
macOS. (Contributed by Donghee Na in bpo-43106.)


os.path
-------

"os.path.realpath()" now accepts a *strict* keyword-only argument.
When set to "True", "OSError" is raised if a path doesn't exist or a
symlink loop is encountered. (Contributed by Barney Gale in
bpo-43757.)


pathlib
-------

Add slice support to "PurePath.parents". (Contributed by Joshua Cannon
in bpo-35498.)

Add negative indexing support to "PurePath.parents". (Contributed by
Yaroslav Pankovych in bpo-21041.)

Add "Path.hardlink_to" method that supersedes "link_to()". The new
method has the same argument order as "symlink_to()". (Contributed by
Barney Gale in bpo-39950.)

"pathlib.Path.stat()" and "chmod()" now accept a *follow_symlinks*
keyword-only argument for consistency with corresponding functions in
the "os" module. (Contributed by Barney Gale in bpo-39906.)


プラットフォーム
----------------

Add "platform.freedesktop_os_release()" to retrieve operation system
identification from freedesktop.org os-release standard file.
(Contributed by Christian Heimes in bpo-28468.)


pprint
------

"pprint.pprint()" now accepts a new "underscore_numbers" keyword
argument. (Contributed by sblondon in bpo-42914.)

"pprint" can now pretty-print "dataclasses.dataclass" instances.
(Contributed by Lewis Gaul in bpo-43080.)


py_compile
----------

Add "--quiet" option to command-line interface of "py_compile".
(Contributed by Gregory Schevchenko in bpo-38731.)


pyclbr
------

Add an "end_lineno" attribute to the "Function" and "Class" objects in
the tree returned by "pyclbr.readmodule()" and
"pyclbr.readmodule_ex()".  It matches the existing (start) "lineno".
(Contributed by Aviral Srivastava in bpo-38307.)


shelve
------

The "shelve" module now uses "pickle.DEFAULT_PROTOCOL" by default
instead of "pickle" protocol "3" when creating shelves. (Contributed
by Zackery Spytz in bpo-34204.)


statistics
----------

Add "covariance()", Pearson's "correlation()", and simple
"linear_regression()" functions. (Contributed by Tymoteusz Wołodźko in
bpo-38490.)


site
----

When a module does not define "__loader__", fall back to
"__spec__.loader". (Contributed by Brett Cannon in bpo-42133.)


socket
------

The exception "socket.timeout" is now an alias of "TimeoutError".
(Contributed by Christian Heimes in bpo-42413.)

Add option to create MPTCP sockets with "IPPROTO_MPTCP" (Contributed
by Rui Cunha in bpo-43571.)

Add "IP_RECVTOS" option to receive the type of service (ToS) or
DSCP/ECN fields (Contributed by Georg Sauthoff in bpo-44077.)


ssl
---

The ssl module requires OpenSSL 1.1.1 or newer. (Contributed by
Christian Heimes in **PEP 644** and bpo-43669.)

The ssl module has preliminary support for OpenSSL 3.0.0 and new
option "OP_IGNORE_UNEXPECTED_EOF". (Contributed by Christian Heimes in
bpo-38820, bpo-43794, bpo-43788, bpo-43791, bpo-43799, bpo-43920,
bpo-43789, and bpo-43811.)

Deprecated function and use of deprecated constants now result in a
"DeprecationWarning". "ssl.SSLContext.options" has "OP_NO_SSLv2" and
"OP_NO_SSLv3" set by default and therefore cannot warn about setting
the flag again. The deprecation section has a list of deprecated
features. (Contributed by Christian Heimes in bpo-43880.)

The ssl module now has more secure default settings. Ciphers without
forward secrecy or SHA-1 MAC are disabled by default. Security level 2
prohibits weak RSA, DH, and ECC keys with less than 112 bits of
security. "SSLContext" defaults to minimum protocol version TLS 1.2.
Settings are based on Hynek Schlawack's research. (Contributed by
Christian Heimes in bpo-43998.)

The deprecated protocols SSL 3.0, TLS 1.0, and TLS 1.1 are no longer
officially supported. Python does not block them actively. However
OpenSSL build options, distro configurations, vendor patches, and
cipher suites may prevent a successful handshake.

Add a *timeout* parameter to the "ssl.get_server_certificate()"
function. (Contributed by Zackery Spytz in bpo-31870.)

The ssl module uses heap-types and multi-phase initialization.
(Contributed by Christian Heimes in bpo-42333.)

A new verify flag "VERIFY_X509_PARTIAL_CHAIN" has been added.
(Contributed by l0x in bpo-40849.)


sqlite3
-------

Add audit events for "connect()", "enable_load_extension()", and
"load_extension()". (Contributed by Erlend E. Aasland in bpo-43762.)


sys
---

Add "sys.orig_argv" attribute: the list of the original command line
arguments passed to the Python executable. (Contributed by Victor
Stinner in bpo-23427.)

Add "sys.stdlib_module_names", containing the list of the standard
library module names. (Contributed by Victor Stinner in bpo-42955.)


_thread
-------

"_thread.interrupt_main()" now takes an optional signal number to
simulate (the default is still "signal.SIGINT"). (Contributed by
Antoine Pitrou in bpo-43356.)


threading
---------

Add "threading.gettrace()" and "threading.getprofile()" to retrieve
the functions set by "threading.settrace()" and
"threading.setprofile()" respectively. (Contributed by Mario Corchero
in bpo-42251.)

Add "threading.__excepthook__" to allow retrieving the original value
of "threading.excepthook()" in case it is set to a broken or a
different value. (Contributed by Mario Corchero in bpo-42308.)


traceback
---------

The "format_exception()", "format_exception_only()", and
"print_exception()" functions can now take an exception object as a
positional-only argument. (Contributed by Zackery Spytz and Matthias
Bussonnier in bpo-26389.)


types
-----

Reintroduce the "types.EllipsisType", "types.NoneType" and
"types.NotImplementedType" classes, providing a new set of types
readily interpretable by type checkers. (Contributed by Bas van Beek
in bpo-41810.)


typing
------

For major changes, see 型ヒントに関連する新しい機能.

The behavior of "typing.Literal" was changed to conform with **PEP
586** and to match the behavior of static type checkers specified in
the PEP.

1. "Literal" now de-duplicates parameters.

2. Equality comparisons between "Literal" objects are now order
   independent.

3. "Literal" comparisons now respect types.  For example, "Literal[0]
   == Literal[False]" previously evaluated to "True".  It is now
   "False".  To support this change, the internally used type cache
   now supports differentiating types.

4. "Literal" objects will now raise a "TypeError" exception during
   equality comparisons if any of their parameters are not *hashable*.
   Note that declaring "Literal" with unhashable parameters will not
   throw an error:

      >>> from typing import Literal
      >>> Literal[{0}]
      >>> Literal[{0}] == Literal[{False}]
      Traceback (most recent call last):
        File "<stdin>", line 1, in <module>
      TypeError: unhashable type: 'set'

(bpo-42345 でのYurii Karabasの貢献による)

Add new function "typing.is_typeddict()" to introspect if an
annotation is a "typing.TypedDict". (Contributed by Patrick Reader in
bpo-41792.)

Subclasses of "typing.Protocol" which only have data variables
declared will now raise a "TypeError" when checked with "isinstance"
unless they are decorated with "@~typing.runtime_checkable".
Previously, these checks passed silently.  Users should decorate their
subclasses with the "@runtime_checkable" decorator if they want
runtime protocols. (Contributed by Yurii Karabas in bpo-38908.)

Importing from the "typing.io" and "typing.re" submodules will now
emit "DeprecationWarning".  These submodules have been deprecated
since Python 3.8 and will be removed in a future version of Python.
Anything belonging to those submodules should be imported directly
from "typing" instead. (Contributed by Sebastian Rittau in bpo-38291.)


unittest
--------

Add new method "assertNoLogs()" to complement the existing
"assertLogs()". (Contributed by Kit Yan Choi in bpo-39385.)


urllib.parse
------------

Python versions earlier than Python 3.10 allowed using both ";" and
"&" as query parameter separators in "urllib.parse.parse_qs()" and
"urllib.parse.parse_qsl()".  Due to security concerns, and to conform
with newer W3C recommendations, this has been changed to allow only a
single separator key, with "&" as the default.  This change also
affects "cgi.parse()" and "cgi.parse_multipart()" as they use the
affected functions internally.  For more details, please see their
respective documentation. (Contributed by Adam Goldschmidt, Senthil
Kumaran and Ken Jin in bpo-42967.)

The presence of newline or tab characters in parts of a URL allows for
some forms of attacks. Following the WHATWG specification that updates
**RFC 3986**, ASCII newline "\n", "\r" and tab "\t" characters are
stripped from the URL by the parser in "urllib.parse" preventing such
attacks. The removal characters are controlled by a new module level
variable "urllib.parse._UNSAFE_URL_BYTES_TO_REMOVE". (See gh-88048)


xml
---

Add a "LexicalHandler" class to the "xml.sax.handler" module.
(Contributed by Jonathan Gossage and Zackery Spytz in bpo-35018.)


zipimport
---------

Add methods related to **PEP 451**: "find_spec()",
"zipimport.zipimporter.create_module()", and
"zipimport.zipimporter.exec_module()". (Contributed by Brett Cannon in
bpo-42131.)

Add "invalidate_caches()" method. (Contributed by Desmond Cheong in
bpo-14678.)


最適化
======

* Constructors "str()", "bytes()" and "bytearray()" are now faster
  (around 30--40% for small objects). (Contributed by Serhiy Storchaka
  in bpo-41334.)

* The "runpy" module now imports fewer modules. The "python3 -m
  module-name" command startup time is 1.4x faster in average. On
  Linux, "python3 -I -m module-name" imports 69 modules on Python 3.9,
  whereas it only imports 51 modules (-18) on Python 3.10.
  (Contributed by Victor Stinner in bpo-41006 and bpo-41718.)

* The "LOAD_ATTR" instruction now uses new "per opcode cache"
  mechanism.  It is about 36% faster now for regular attributes and
  44% faster for slots. (Contributed by Pablo Galindo and Yury
  Selivanov in bpo-42093 and Guido van Rossum in bpo-42927, based on
  ideas implemented originally in PyPy and MicroPython.)

* When building Python with "--enable-optimizations" now "-fno-
  semantic-interposition" is added to both the compile and link line.
  This speeds builds of the Python interpreter created with "--enable-
  shared" with "gcc" by up to 30%. See this article for more details.
  (Contributed by Victor Stinner and Pablo Galindo in bpo-38980.)

* Use a new output buffer management code for "bz2" / "lzma" / "zlib"
  modules, and add ".readall()" function to
  "_compression.DecompressReader" class. bz2 decompression is now
  1.09x ~ 1.17x faster, lzma decompression 1.20x ~ 1.32x faster,
  "GzipFile.read(-1)" 1.11x ~ 1.18x faster. (Contributed by Ma Lin,
  reviewed by Gregory P. Smith, in bpo-41486)

* When using stringized annotations, annotations dicts for functions
  are no longer created when the function is created.  Instead, they
  are stored as a tuple of strings, and the function object lazily
  converts this into the annotations dict on demand.  This
  optimization cuts the CPU time needed to define an annotated
  function by half. (Contributed by Yurii Karabas and Inada Naoki in
  bpo-42202.)

* Substring search functions such as "str1 in str2" and
  "str2.find(str1)" now sometimes use Crochemore & Perrin's "Two-Way"
  string searching algorithm to avoid quadratic behavior on long
  strings.  (Contributed by Dennis Sweeney in bpo-41972)

* Add micro-optimizations to "_PyType_Lookup()" to improve type
  attribute cache lookup performance in the common case of cache hits.
  This makes the interpreter 1.04 times faster on average.
  (Contributed by Dino Viehland in bpo-43452.)

* The following built-in functions now support the faster **PEP 590**
  vectorcall calling convention: "map()", "filter()", "reversed()",
  "bool()" and "float()". (Contributed by Donghee Na and Jeroen
  Demeyer in bpo-43575, bpo-43287, bpo-41922, bpo-41873 and
  bpo-41870.)

* "BZ2File" performance is improved by removing internal "RLock". This
  makes "BZ2File" thread unsafe in the face of multiple simultaneous
  readers or writers, just like its equivalent classes in "gzip" and
  "lzma" have always been.  (Contributed by Inada Naoki in bpo-43785.)


非推奨
======

* Currently Python accepts numeric literals immediately followed by
  keywords, for example "0in x", "1or x", "0if 1else 2".  It allows
  confusing and ambiguous expressions like "[0x1for x in y]" (which
  can be interpreted as "[0x1 for x in y]" or "[0x1f or x in y]").
  Starting in this release, a deprecation warning is raised if the
  numeric literal is immediately followed by one of keywords "and",
  "else", "for", "if", "in", "is" and "or". In future releases it will
  be changed to syntax warning, and finally to syntax error.
  (Contributed by Serhiy Storchaka in bpo-43833.)

* Starting in this release, there will be a concerted effort to begin
  cleaning up old import semantics that were kept for Python 2.7
  compatibility. Specifically, "find_loader()"/"find_module()"
  (superseded by "find_spec()"), "load_module()" (superseded by
  "exec_module()"), "module_repr()" (which the import system takes
  care of for you), the "__package__" attribute (superseded by
  "__spec__.parent"), the "__loader__" attribute (superseded by
  "__spec__.loader"), and the "__cached__" attribute (superseded by
  "__spec__.cached") will slowly be removed (as well as other classes
  and methods in "importlib"). "ImportWarning" and/or
  "DeprecationWarning" will be raised as appropriate to help identify
  code which needs updating during this transition.

* The entire "distutils" namespace is deprecated, to be removed in
  Python 3.12. Refer to the module changes section for more
  information.

* Non-integer arguments to "random.randrange()" are deprecated. The
  "ValueError" is deprecated in favor of a "TypeError". (Contributed
  by Serhiy Storchaka and Raymond Hettinger in bpo-37319.)

* The various "load_module()" methods of "importlib" have been
  documented as deprecated since Python 3.6, but will now also trigger
  a "DeprecationWarning". Use "exec_module()" instead. (Contributed by
  Brett Cannon in bpo-26131.)

* "zimport.zipimporter.load_module()" has been deprecated in
  preference for "exec_module()". (Contributed by Brett Cannon in
  bpo-26131.)

* The use of "load_module()" by the import system now triggers an
  "ImportWarning" as "exec_module()" is preferred. (Contributed by
  Brett Cannon in bpo-26131.)

* The use of "importlib.abc.MetaPathFinder.find_module()" and
  "importlib.abc.PathEntryFinder.find_module()" by the import system
  now trigger an "ImportWarning" as
  "importlib.abc.MetaPathFinder.find_spec()" and
  "importlib.abc.PathEntryFinder.find_spec()" are preferred,
  respectively. You can use "importlib.util.spec_from_loader()" to
  help in porting. (Contributed by Brett Cannon in bpo-42134.)

* The use of "importlib.abc.PathEntryFinder.find_loader()" by the
  import system now triggers an "ImportWarning" as
  "importlib.abc.PathEntryFinder.find_spec()" is preferred. You can
  use "importlib.util.spec_from_loader()" to help in porting.
  (Contributed by Brett Cannon in bpo-43672.)

* The various implementations of
  "importlib.abc.MetaPathFinder.find_module()" (
  "importlib.machinery.BuiltinImporter.find_module()",
  "importlib.machinery.FrozenImporter.find_module()",
  "importlib.machinery.WindowsRegistryFinder.find_module()",
  "importlib.machinery.PathFinder.find_module()",
  "importlib.abc.MetaPathFinder.find_module()" ),
  "importlib.abc.PathEntryFinder.find_module()" (
  "importlib.machinery.FileFinder.find_module()" ), and
  "importlib.abc.PathEntryFinder.find_loader()" (
  "importlib.machinery.FileFinder.find_loader()" ) now raise
  "DeprecationWarning" and are slated for removal in Python 3.12
  (previously they were documented as deprecated in Python 3.4).
  (Contributed by Brett Cannon in bpo-42135.)

* "importlib.abc.Finder" is deprecated (including its sole method,
  "find_module()"). Both "importlib.abc.MetaPathFinder" and
  "importlib.abc.PathEntryFinder" no longer inherit from the class.
  Users should inherit from one of these two classes as appropriate
  instead. (Contributed by Brett Cannon in bpo-42135.)

* The deprecations of "imp", "importlib.find_loader()",
  "importlib.util.set_package_wrapper()",
  "importlib.util.set_loader_wrapper()",
  "importlib.util.module_for_loader()", "pkgutil.ImpImporter", and
  "pkgutil.ImpLoader" have all been updated to list Python 3.12 as the
  slated version of removal (they began raising "DeprecationWarning"
  in previous versions of Python). (Contributed by Brett Cannon in
  bpo-43720.)

* The import system now uses the "__spec__" attribute on modules
  before falling back on "module_repr()" for a module's "__repr__()"
  method. Removal of the use of "module_repr()" is scheduled for
  Python 3.12. (Contributed by Brett Cannon in bpo-42137.)

* "importlib.abc.Loader.module_repr()",
  "importlib.machinery.FrozenLoader.module_repr()", and
  "importlib.machinery.BuiltinLoader.module_repr()" are deprecated and
  slated for removal in Python 3.12. (Contributed by Brett Cannon in
  bpo-42136.)

* "sqlite3.OptimizedUnicode" has been undocumented and obsolete since
  Python 3.3, when it was made an alias to "str".  It is now
  deprecated, scheduled for removal in Python 3.12. (Contributed by
  Erlend E. Aasland in bpo-42264.)

* The undocumented built-in function "sqlite3.enable_shared_cache" is
  now deprecated, scheduled for removal in Python 3.12.  Its use is
  strongly discouraged by the SQLite3 documentation.  See the SQLite3
  docs for more details. If a shared cache must be used, open the
  database in URI mode using the "cache=shared" query parameter.
  (Contributed by Erlend E. Aasland in bpo-24464.)

* 以下の "threading" メソッドは非推奨になりました：

  * "threading.currentThread" => "threading.current_thread()"

  * "threading.activeCount" => "threading.active_count()"

  * "threading.Condition.notifyAll" =>
    "threading.Condition.notify_all()"

  * "threading.Event.isSet" => "threading.Event.is_set()"

  * "threading.Thread.setName" => "threading.Thread.name"

  * "threading.thread.getName" => "threading.Thread.name"

  * "threading.Thread.isDaemon" => "threading.Thread.daemon"

  * "threading.Thread.setDaemon" => "threading.Thread.daemon"

  (Contributed by Jelle Zijlstra in gh-87889.)

* "pathlib.Path.link_to()" is deprecated and slated for removal in
  Python 3.12. Use "pathlib.Path.hardlink_to()" instead. (Contributed
  by Barney Gale in bpo-39950.)

* "cgi.log()" is deprecated and slated for removal in Python 3.12.
  (Contributed by Inada Naoki in bpo-41139.)

* The following "ssl" features have been deprecated since Python 3.6,
  Python 3.7, or OpenSSL 1.1.0 and will be removed in 3.11:

  * "OP_NO_SSLv2", "OP_NO_SSLv3", "OP_NO_TLSv1", "OP_NO_TLSv1_1",
    "OP_NO_TLSv1_2", and "OP_NO_TLSv1_3" are replaced by
    "minimum_version" and "maximum_version".

  * "PROTOCOL_SSLv2", "PROTOCOL_SSLv3", "PROTOCOL_SSLv23",
    "PROTOCOL_TLSv1", "PROTOCOL_TLSv1_1", "PROTOCOL_TLSv1_2", and
    "PROTOCOL_TLS" are deprecated in favor of "PROTOCOL_TLS_CLIENT"
    and "PROTOCOL_TLS_SERVER"

  * "wrap_socket()" is replaced by "ssl.SSLContext.wrap_socket()"

  * "match_hostname()"

  * "RAND_pseudo_bytes()", "RAND_egd()"

  * NPN features like "ssl.SSLSocket.selected_npn_protocol()" and
    "ssl.SSLContext.set_npn_protocols()" are replaced by ALPN.

* The threading debug ("PYTHONTHREADDEBUG" environment variable) is
  deprecated in Python 3.10 and will be removed in Python 3.12. This
  feature requires a debug build of Python. (Contributed by Victor
  Stinner in bpo-44584.)

* Importing from the "typing.io" and "typing.re" submodules will now
  emit "DeprecationWarning".  These submodules will be removed in a
  future version of Python.  Anything belonging to these submodules
  should be imported directly from "typing" instead. (Contributed by
  Sebastian Rittau in bpo-38291.)


削除
====

* Removed special methods "__int__", "__float__", "__floordiv__",
  "__mod__", "__divmod__", "__rfloordiv__", "__rmod__" and
  "__rdivmod__" of the "complex" class.  They always raised a
  "TypeError". (Contributed by Serhiy Storchaka in bpo-41974.)

* The "ParserBase.error()" method from the private and undocumented
  "_markupbase" module has been removed.  "html.parser.HTMLParser" is
  the only subclass of "ParserBase" and its "error()" implementation
  was already removed in Python 3.5. (Contributed by Berker Peksag in
  bpo-31844.)

* Removed the "unicodedata.ucnhash_CAPI" attribute which was an
  internal PyCapsule object. The related private
  "_PyUnicode_Name_CAPI" structure was moved to the internal C API.
  (Contributed by Victor Stinner in bpo-42157.)

* Removed the "parser" module, which was deprecated in 3.9 due to the
  switch to the new PEG parser, as well as all the C source and header
  files that were only being used by the old parser, including
  "node.h", "parser.h", "graminit.h" and "grammar.h".

* Removed the Public C API functions
  "PyParser_SimpleParseStringFlags",
  "PyParser_SimpleParseStringFlagsFilename",
  "PyParser_SimpleParseFileFlags" and "PyNode_Compile" that were
  deprecated in 3.9 due to the switch to the new PEG parser.

* Removed the "formatter" module, which was deprecated in Python 3.4.
  It is somewhat obsolete, little used, and not tested. It was
  originally scheduled to be removed in Python 3.6, but such removals
  were delayed until after Python 2.7 EOL. Existing users should copy
  whatever classes they use into their code. (Contributed by Donghee
  Na and Terry J. Reedy in bpo-42299.)

* Removed the "PyModule_GetWarningsModule()" function that was useless
  now due to the "_warnings" module was converted to a builtin module
  in 2.6. (Contributed by Hai Shi in bpo-42599.)

* Remove deprecated aliases to コレクション抽象基底クラス from the
  "collections" module. (Contributed by Victor Stinner in bpo-37324.)

* The "loop" parameter has been removed from most of "asyncio"'s high-
  level API following deprecation in Python 3.8.  The motivation
  behind this change is multifold:

  1. This simplifies the high-level API.

  2. The functions in the high-level API have been implicitly getting
     the current thread's running event loop since Python 3.7.  There
     isn't a need to pass the event loop to the API in most normal use
     cases.

  3. Event loop passing is error-prone especially when dealing with
     loops running in different threads.

  Note that the low-level API will still accept "loop". See Python API
  の変更 for examples of how to replace existing code.

  (Contributed by Yurii Karabas, Andrew Svetlov, Yury Selivanov and
  Kyle Stanley in bpo-42392.)


Porting to Python 3.10
======================

このセクションでは前述の変更とバグフィックスにより必要となるかもしれな
いコードの変更を列挙します:


Changes in the Python syntax
----------------------------

* Deprecation warning is now emitted when compiling previously valid
  syntax if the numeric literal is immediately followed by a keyword
  (like in "0in x"). In future releases it will be changed to syntax
  warning, and finally to a syntax error.  To get rid of the warning
  and make the code compatible with future releases just add a space
  between the numeric literal and the following keyword. (Contributed
  by Serhiy Storchaka in bpo-43833.)


Python API の変更
-----------------

* The *etype* parameters of the "format_exception()",
  "format_exception_only()", and "print_exception()" functions in the
  "traceback" module have been renamed to *exc*. (Contributed by
  Zackery Spytz and Matthias Bussonnier in bpo-26389.)

* "atexit": At Python exit, if a callback registered with
  "atexit.register()" fails, its exception is now logged. Previously,
  only some exceptions were logged, and the last exception was always
  silently ignored. (Contributed by Victor Stinner in bpo-42639.)

* "collections.abc.Callable" generic now flattens type parameters,
  similar to what "typing.Callable" currently does.  This means that
  "collections.abc.Callable[[int, str], str]" will have "__args__" of
  "(int, str, str)"; previously this was "([int, str], str)".  Code
  which accesses the arguments via "typing.get_args()" or "__args__"
  need to account for this change.  Furthermore, "TypeError" may be
  raised for invalid forms of parameterizing
  "collections.abc.Callable" which may have passed silently in Python
  3.9. (Contributed by Ken Jin in bpo-42195.)

* "socket.htons()" and "socket.ntohs()" now raise "OverflowError"
  instead of "DeprecationWarning" if the given parameter will not fit
  in a 16-bit unsigned integer. (Contributed by Erlend E. Aasland in
  bpo-42393.)

* The "loop" parameter has been removed from most of "asyncio"'s high-
  level API following deprecation in Python 3.8.

  A coroutine that currently looks like this:

     async def foo(loop):
         await asyncio.sleep(1, loop=loop)

  Should be replaced with this:

     async def foo():
         await asyncio.sleep(1)

  If "foo()" was specifically designed *not* to run in the current
  thread's running event loop (e.g. running in another thread's event
  loop), consider using "asyncio.run_coroutine_threadsafe()" instead.

  (Contributed by Yurii Karabas, Andrew Svetlov, Yury Selivanov and
  Kyle Stanley in bpo-42392.)

* The "types.FunctionType" constructor now inherits the current
  builtins if the *globals* dictionary has no ""__builtins__"" key,
  rather than using "{"None": None}" as builtins: same behavior as
  "eval()" and "exec()" functions.  Defining a function with "def
  function(...): ..." in Python is not affected, globals cannot be
  overridden with this syntax: it also inherits the current builtins.
  (Contributed by Victor Stinner in bpo-42990.)


C API の変更
------------

* The C API functions "PyParser_SimpleParseStringFlags",
  "PyParser_SimpleParseStringFlagsFilename",
  "PyParser_SimpleParseFileFlags", "PyNode_Compile" and the type used
  by these functions, "struct _node", were removed due to the switch
  to the new PEG parser.

  Source should be now be compiled directly to a code object using,
  for example, "Py_CompileString()". The resulting code object can
  then be evaluated using, for example, "PyEval_EvalCode()".

  Specifically:

  * A call to "PyParser_SimpleParseStringFlags" followed by
    "PyNode_Compile" can be replaced by calling "Py_CompileString()".

  * There is no direct replacement for
    "PyParser_SimpleParseFileFlags". To compile code from a "FILE *"
    argument, you will need to read the file in C and pass the
    resulting buffer to "Py_CompileString()".

  * To compile a file given a "char *" filename, explicitly open the
    file, read it and compile the result. One way to do this is using
    the "io" module with "PyImport_ImportModule()",
    "PyObject_CallMethod()", "PyBytes_AsString()" and
    "Py_CompileString()", as sketched below. (Declarations and error
    handling are omitted.)

       io_module = Import_ImportModule("io");
       fileobject = PyObject_CallMethod(io_module, "open", "ss", filename, "rb");
       source_bytes_object = PyObject_CallMethod(fileobject, "read", "");
       result = PyObject_CallMethod(fileobject, "close", "");
       source_buf = PyBytes_AsString(source_bytes_object);
       code = Py_CompileString(source_buf, filename, Py_file_input);

  * For "FrameObject" objects, the "f_lasti" member now represents a
    wordcode offset instead of a simple offset into the bytecode
    string. This means that this number needs to be multiplied by 2 to
    be used with APIs that expect a byte offset instead (like
    "PyCode_Addr2Line()" for example). Notice as well that the
    "f_lasti" member of "FrameObject" objects is not considered
    stable: please use "PyFrame_GetLineNumber()" instead.


CPython バイトコードの変更
==========================

* The "MAKE_FUNCTION" instruction now accepts either a dict or a tuple
  of strings as the function's annotations. (Contributed by Yurii
  Karabas and Inada Naoki in bpo-42202.)


Build Changes
=============

* **PEP 644**: Python now requires OpenSSL 1.1.1 or newer. OpenSSL
  1.0.2 is no longer supported. (Contributed by Christian Heimes in
  bpo-43669.)

* The C99 functions "snprintf()" and "vsnprintf()" are now required to
  build Python. (Contributed by Victor Stinner in bpo-36020.)

* "sqlite3" requires SQLite 3.7.15 or higher. (Contributed by Sergey
  Fedoseev and Erlend E. Aasland in bpo-40744 and bpo-40810.)

* The "atexit" module must now always be built as a built-in module.
  (Contributed by Victor Stinner in bpo-42639.)

* Add "--disable-test-modules" option to the "configure" script: don't
  build nor install test modules. (Contributed by Xavier de Gaye,
  Thomas Petazzoni and Peixing Xin in bpo-27640.)

* Add "--with-wheel-pkg-dir=PATH option" to the "./configure" script.
  If specified, the "ensurepip" module looks for "setuptools" and
  "pip" wheel packages in this directory: if both are present, these
  wheel packages are used instead of ensurepip bundled wheel packages.

  Some Linux distribution packaging policies recommend against
  bundling dependencies. For example, Fedora installs wheel packages
  in the "/usr/share/python-wheels/" directory and don't install the
  "ensurepip._bundled" package.

  (Contributed by Victor Stinner in bpo-42856.)

* Add a new "configure --without-static-libpython option" to not build
  the "libpythonMAJOR.MINOR.a" static library and not install the
  "python.o" object file.

  (Contributed by Victor Stinner in bpo-43103.)

* The "configure" script now uses the "pkg-config" utility, if
  available, to detect the location of Tcl/Tk headers and libraries.
  As before, those locations can be explicitly specified with the "--
  with-tcltk-includes" and "--with-tcltk-libs" configuration options.
  (Contributed by Manolis Stamatogiannakis in bpo-42603.)

* Add "--with-openssl-rpath" option to "configure" script. The option
  simplifies building Python with a custom OpenSSL installation, e.g.
  "./configure --with-openssl=/path/to/openssl --with-openssl-
  rpath=auto". (Contributed by Christian Heimes in bpo-43466.)


C API の変更
============


PEP 652: Maintaining the Stable ABI
-----------------------------------

The Stable ABI (Application Binary Interface) for extension modules or
embedding Python is now explicitly defined. C API Stability describes
C API and ABI stability guarantees along with best practices for using
the Stable ABI.

(Contributed by Petr Viktorin in **PEP 652** and bpo-43795.)


新しい機能
----------

* The result of "PyNumber_Index()" now always has exact type "int".
  Previously, the result could have been an instance of a subclass of
  "int". (Contributed by Serhiy Storchaka in bpo-40792.)

* Add a new "orig_argv" member to the "PyConfig" structure: the list
  of the original command line arguments passed to the Python
  executable. (Contributed by Victor Stinner in bpo-23427.)

* The "PyDateTime_DATE_GET_TZINFO()" and
  "PyDateTime_TIME_GET_TZINFO()" macros have been added for accessing
  the "tzinfo" attributes of "datetime.datetime" and "datetime.time"
  objects. (Contributed by Zackery Spytz in bpo-30155.)

* Add a "PyCodec_Unregister()" function to unregister a codec search
  function. (Contributed by Hai Shi in bpo-41842.)

* The "PyIter_Send()" function was added to allow sending value into
  iterator without raising "StopIteration" exception. (Contributed by
  Vladimir Matveev in bpo-41756.)

* Add "PyUnicode_AsUTF8AndSize()" to the limited C API. (Contributed
  by Alex Gaynor in bpo-41784.)

* Add "PyModule_AddObjectRef()" function: similar to
  "PyModule_AddObject()" but don't steal a reference to the value on
  success. (Contributed by Victor Stinner in bpo-1635741.)

* Add "Py_NewRef()" and "Py_XNewRef()" functions to increment the
  reference count of an object and return the object. (Contributed by
  Victor Stinner in bpo-42262.)

* The "PyType_FromSpecWithBases()" and "PyType_FromModuleAndSpec()"
  functions now accept a single class as the *bases* argument.
  (Contributed by Serhiy Storchaka in bpo-42423.)

* The "PyType_FromModuleAndSpec()" function now accepts NULL "tp_doc"
  slot. (Contributed by Hai Shi in bpo-41832.)

* The "PyType_GetSlot()" function can accept static types.
  (Contributed by Hai Shi and Petr Viktorin in bpo-41073.)

* Add a new "PySet_CheckExact()" function to the C-API to check if an
  object is an instance of "set" but not an instance of a subtype.
  (Contributed by Pablo Galindo in bpo-43277.)

* Add "PyErr_SetInterruptEx()" which allows passing a signal number to
  simulate. (Contributed by Antoine Pitrou in bpo-43356.)

* The limited C API is now supported if Python is built in debug mode
  (if the "Py_DEBUG" macro is defined). In the limited C API, the
  "Py_INCREF()" and "Py_DECREF()" functions are now implemented as
  opaque function calls, rather than accessing directly the
  "PyObject.ob_refcnt" member, if Python is built in debug mode and
  the "Py_LIMITED_API" macro targets Python 3.10 or newer. It became
  possible to support the limited C API in debug mode because the
  "PyObject" structure is the same in release and debug mode since
  Python 3.8 (see bpo-36465).

  The limited C API is still not supported in the "--with-trace-refs"
  special build ("Py_TRACE_REFS" macro). (Contributed by Victor
  Stinner in bpo-43688.)

* Add the "Py_Is(x, y)" function to test if the *x* object is the *y*
  object, the same as "x is y" in Python. Add also the "Py_IsNone()",
  "Py_IsTrue()", "Py_IsFalse()" functions to test if an object is,
  respectively, the "None" singleton, the "True" singleton or the
  "False" singleton. (Contributed by Victor Stinner in bpo-43753.)

* Add new functions to control the garbage collector from C code:
  "PyGC_Enable()", "PyGC_Disable()", "PyGC_IsEnabled()". These
  functions allow to activate, deactivate and query the state of the
  garbage collector from C code without having to import the "gc"
  module.

* Add a new "Py_TPFLAGS_DISALLOW_INSTANTIATION" type flag to disallow
  creating type instances. (Contributed by Victor Stinner in
  bpo-43916.)

* Add a new "Py_TPFLAGS_IMMUTABLETYPE" type flag for creating
  immutable type objects: type attributes cannot be set nor deleted.
  (Contributed by Victor Stinner and Erlend E. Aasland in bpo-43908.)


Porting to Python 3.10
----------------------

* The "PY_SSIZE_T_CLEAN" macro must now be defined to use
  "PyArg_ParseTuple()" and "Py_BuildValue()" formats which use "#":
  "es#", "et#", "s#", "u#", "y#", "z#", "U#" and "Z#". See 引数の解釈
  と値の構築 and **PEP 353**. (Contributed by Victor Stinner in
  bpo-40943.)

* Since "Py_REFCNT()" is changed to the inline static function,
  "Py_REFCNT(obj) = new_refcnt" must be replaced with
  "Py_SET_REFCNT(obj, new_refcnt)": see "Py_SET_REFCNT()" (available
  since Python 3.9). For backward compatibility, this macro can be
  used:

     #if PY_VERSION_HEX < 0x030900A4
     #  define Py_SET_REFCNT(obj, refcnt) ((Py_REFCNT(obj) = (refcnt)), (void)0)
     #endif

  (Contributed by Victor Stinner in bpo-39573.)

* Calling "PyDict_GetItem()" without *GIL* held had been allowed for
  historical reason. It is no longer allowed. (Contributed by Victor
  Stinner in bpo-40839.)

* "PyUnicode_FromUnicode(NULL, size)" and
  "PyUnicode_FromStringAndSize(NULL, size)" raise "DeprecationWarning"
  now.  Use "PyUnicode_New()" to allocate Unicode object without
  initial data. (Contributed by Inada Naoki in bpo-36346.)

* The private "_PyUnicode_Name_CAPI" structure of the PyCapsule API
  "unicodedata.ucnhash_CAPI" has been moved to the internal C API.
  (Contributed by Victor Stinner in bpo-42157.)

* "Py_GetPath()", "Py_GetPrefix()", "Py_GetExecPrefix()",
  "Py_GetProgramFullPath()", "Py_GetPythonHome()" and
  "Py_GetProgramName()" functions now return "NULL" if called before
  "Py_Initialize()" (before Python is initialized). Use the new Python
  初期化設定 API to get the Python Path Configuration. (Contributed by
  Victor Stinner in bpo-42260.)

* "PyList_SET_ITEM()", "PyTuple_SET_ITEM()" and "PyCell_SET()" macros
  can no longer be used as l-value or r-value. For example, "x =
  PyList_SET_ITEM(a, b, c)" and "PyList_SET_ITEM(a, b, c) = x" now
  fail with a compiler error. It prevents bugs like "if
  (PyList_SET_ITEM (a, b, c) < 0) ..." test. (Contributed by Zackery
  Spytz and Victor Stinner in bpo-30459.)

* The non-limited API files "odictobject.h", "parser_interface.h",
  "picklebufobject.h", "pyarena.h", "pyctype.h", "pydebug.h",
  "pyfpe.h", and "pytime.h" have been moved to the "Include/cpython"
  directory. These files must not be included directly, as they are
  already included in "Python.h"; see インクルードファイル. If they
  have been included directly, consider including "Python.h" instead.
  (Contributed by Nicholas Sim in bpo-35134.)

* Use the "Py_TPFLAGS_IMMUTABLETYPE" type flag to create immutable
  type objects. Do not rely on "Py_TPFLAGS_HEAPTYPE" to decide if a
  type object is mutable or not; check if "Py_TPFLAGS_IMMUTABLETYPE"
  is set instead. (Contributed by Victor Stinner and Erlend E. Aasland
  in bpo-43908.)

* The undocumented function "Py_FrozenMain" has been removed from the
  limited API. The function is mainly useful for custom builds of
  Python. (Contributed by Petr Viktorin in bpo-26241.)


非推奨
------

* The "PyUnicode_InternImmortal()" function is now deprecated and will
  be removed in Python 3.12: use "PyUnicode_InternInPlace()" instead.
  (Contributed by Victor Stinner in bpo-41692.)


削除
----

* Removed "Py_UNICODE_str*" functions manipulating "Py_UNICODE*"
  strings. (Contributed by Inada Naoki in bpo-41123.)

  * "Py_UNICODE_strlen": use "PyUnicode_GetLength()" or
    "PyUnicode_GET_LENGTH"

  * "Py_UNICODE_strcat": use "PyUnicode_CopyCharacters()" or
    "PyUnicode_FromFormat()"

  * "Py_UNICODE_strcpy", "Py_UNICODE_strncpy": use
    "PyUnicode_CopyCharacters()" or "PyUnicode_Substring()"

  * "Py_UNICODE_strcmp": use "PyUnicode_Compare()"

  * "Py_UNICODE_strncmp": use "PyUnicode_Tailmatch()"

  * "Py_UNICODE_strchr", "Py_UNICODE_strrchr": use
    "PyUnicode_FindChar()"

* Removed "PyUnicode_GetMax()". Please migrate to new (**PEP 393**)
  APIs. (Contributed by Inada Naoki in bpo-41103.)

* Removed "PyLong_FromUnicode()". Please migrate to
  "PyLong_FromUnicodeObject()". (Contributed by Inada Naoki in
  bpo-41103.)

* Removed "PyUnicode_AsUnicodeCopy()". Please use
  "PyUnicode_AsUCS4Copy()" or "PyUnicode_AsWideCharString()"
  (Contributed by Inada Naoki in bpo-41103.)

* Removed "_Py_CheckRecursionLimit" variable: it has been replaced by
  "ceval.recursion_limit" of the "PyInterpreterState" structure.
  (Contributed by Victor Stinner in bpo-41834.)

* Removed undocumented macros "Py_ALLOW_RECURSION" and
  "Py_END_ALLOW_RECURSION" and the "recursion_critical" field of the
  "PyInterpreterState" structure. (Contributed by Serhiy Storchaka in
  bpo-41936.)

* Removed the undocumented "PyOS_InitInterrupts()" function.
  Initializing Python already implicitly installs signal handlers: see
  "PyConfig.install_signal_handlers". (Contributed by Victor Stinner
  in bpo-41713.)

* Remove the "PyAST_Validate()" function. It is no longer possible to
  build a AST object ("mod_ty" type) with the public C API. The
  function was already excluded from the limited C API (**PEP 384**).
  (Contributed by Victor Stinner in bpo-43244.)

* Remove the "symtable.h" header file and the undocumented functions:

  * "PyST_GetScope()"

  * "PySymtable_Build()"

  * "PySymtable_BuildObject()"

  * "PySymtable_Free()"

  * "Py_SymtableString()"

  * "Py_SymtableStringObject()"

  The "Py_SymtableString()" function was part the stable ABI by
  mistake but it could not be used, because the "symtable.h" header
  file was excluded from the limited C API.

  Use Python "symtable" module instead. (Contributed by Victor Stinner
  in bpo-43244.)

* Remove "PyOS_ReadlineFunctionPointer()" from the limited C API
  headers and from "python3.dll", the library that provides the stable
  ABI on Windows. Since the function takes a "FILE*" argument, its ABI
  stability cannot be guaranteed. (Contributed by Petr Viktorin in
  bpo-43868.)

* Remove "ast.h", "asdl.h", and "Python-ast.h" header files. These
  functions were undocumented and excluded from the limited C API.
  Most names defined by these header files were not prefixed by "Py"
  and so could create names conflicts. For example, "Python-ast.h"
  defined a "Yield" macro which was conflict with the "Yield" name
  used by the Windows "<winbase.h>" header. Use the Python "ast"
  module instead. (Contributed by Victor Stinner in bpo-43244.)

* Remove the compiler and parser functions using "struct _mod" type,
  because the public AST C API was removed:

  * "PyAST_Compile()"

  * "PyAST_CompileEx()"

  * "PyAST_CompileObject()"

  * "PyFuture_FromAST()"

  * "PyFuture_FromASTObject()"

  * "PyParser_ASTFromFile()"

  * "PyParser_ASTFromFileObject()"

  * "PyParser_ASTFromFilename()"

  * "PyParser_ASTFromString()"

  * "PyParser_ASTFromStringObject()"

  These functions were undocumented and excluded from the limited C
  API. (Contributed by Victor Stinner in bpo-43244.)

* Remove the "pyarena.h" header file with functions:

  * "PyArena_New()"

  * "PyArena_Free()"

  * "PyArena_Malloc()"

  * "PyArena_AddPyObject()"

  These functions were undocumented, excluded from the limited C API,
  and were only used internally by the compiler. (Contributed by
  Victor Stinner in bpo-43244.)

* The "PyThreadState.use_tracing" member has been removed to optimize
  Python. (Contributed by Mark Shannon in bpo-43760.)


Notable security feature in 3.10.7
==================================

Converting between "int" and "str" in bases other than 2 (binary), 4,
8 (octal), 16 (hexadecimal), or 32 such as base 10 (decimal) now
raises a "ValueError" if the number of digits in string form is above
a limit to avoid potential denial of service attacks due to the
algorithmic complexity. This is a mitigation for **CVE 2020-10735**.
This limit can be configured or disabled by environment variable,
command line flag, or "sys" APIs. See the integer string conversion
length limitation documentation.  The default limit is 4300 digits in
string form.


Notable security feature in 3.10.8
==================================

The deprecated "mailcap" module now refuses to inject unsafe text
(filenames, MIME types, parameters) into shell commands. Instead of
using such text, it will warn and act as if a match was not found (or
for test commands, as if the test failed). (Contributed by Petr
Viktorin in gh-98966.)


Notable changes in 3.10.12
==========================


tarfile
-------

* The extraction methods in "tarfile", and "shutil.unpack_archive()",
  have a new a *filter* argument that allows limiting tar features
  than may be surprising or dangerous, such as creating files outside
  the destination directory. See Extraction filters for details. In
  Python 3.12, use without the *filter* argument will show a
  "DeprecationWarning". In Python 3.14, the default will switch to
  "'data'". (Contributed by Petr Viktorin in **PEP 706**.)
