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What’s New In Python 3.10

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What’s New In Python 3.10

What’s New In Python 3.10 ¶

编者 :: Pablo Galindo Salgado

This article explains the new features in Python 3.10, compared to 3.9. Python 3.10 was released on October 4, 2021. For full details, see the changelog .

摘要 – 发行亮点 ¶

新句法特征：

PEP 634 , Structural Pattern Matching: Specification
PEP 635 , Structural Pattern Matching: Motivation and Rationale
PEP 636 , Structural Pattern Matching: Tutorial
bpo-12782 , Parenthesized context managers are now officially allowed.

新的标准库特征：

PEP 618 , Add Optional Length-Checking To zip.

解释器改进：

PEP 626 , Precise line numbers for debugging and other tools.

新类型特征：

PEP 604 , Allow writing union types as X | Y
PEP 612 , Parameter Specification Variables
PEP 613 , Explicit Type Aliases
PEP 647 , User-Defined Type Guards

Important deprecations, removals or restrictions:

PEP 644 , Require OpenSSL 1.1.1 or newer
PEP 632 , Deprecate distutils module.
PEP 623 , Deprecate and prepare for the removal of the wstr member in PyUnicodeObject.
PEP 624 , Remove Py_UNICODE encoder APIs
PEP 597 , Add optional EncodingWarning

新特征 ¶

Parenthesized context managers ¶

Using enclosing parentheses for continuation across multiple lines in context managers is now supported. This allows formatting a long collection of context managers in multiple lines in a similar way as it was previously possible with import statements. For instance, all these examples are now valid:

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

it is also possible to use a trailing comma at the end of the enclosed group:

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

This new syntax uses the non LL(1) capacities of the new parser. Check PEP 617 了解更多细节。

(Contributed by Guido van Rossum, Pablo Galindo and Lysandros Nikolaou in bpo-12782 and bpo-40334 )。

Better error messages ¶

SyntaxErrors ¶

When parsing code that contains unclosed parentheses or brackets the interpreter now includes the location of the unclosed bracket of parentheses instead of displaying SyntaxError: unexpected EOF while parsing or pointing to some incorrect location. For instance, consider the following code (notice the unclosed ‘{‘):

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()

Previous versions of the interpreter reported confusing places as the location of the syntax error:

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

but in Python 3.10 a more informative error is emitted:

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

In a similar way, errors involving unclosed string literals (single and triple quoted) now point to the start of the string instead of reporting EOF/EOL.

These improvements are inspired by previous work in the PyPy interpreter.

(Contributed by Pablo Galindo in bpo-42864 and Batuhan Taskaya in bpo-40176 )。

SyntaxError exceptions raised by the interpreter will now highlight the full error range of the expression that constitutes the syntax error itself, instead of just where the problem is detected. In this way, instead of displaying (before Python 3.10):

>>> 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

now Python 3.10 will display the exception as:

>>> 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

This improvement was contributed by Pablo Galindo in bpo-43914 .

A considerable amount of new specialized messages for SyntaxError exceptions have been incorporated. Some of the most notable ones are as follows:

Missing : before blocks:

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

(Contributed by Pablo Galindo in bpo-42997 )。

Unparenthesised tuples in comprehensions targets:

>>> {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?

(Contributed by Pablo Galindo in bpo-43017 )。

Missing commas in collection literals and between expressions:

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

(Contributed by Pablo Galindo in bpo-43822 )。

Multiple Exception types without parentheses:

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

(Contributed by Pablo Galindo in bpo-43149 )。

Missing : and values in dictionary literals:

>>> 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

(Contributed by Pablo Galindo in bpo-43823 )。

try blocks without except or finally 块：

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

(Contributed by Pablo Galindo in bpo-44305 )。

Usage of = 而不是 == in comparisons:

>>> 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 '='?

(Contributed by Pablo Galindo in bpo-43797 )。

Usage of * in f-strings:

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

(Contributed by Pablo Galindo in bpo-41064 )。

IndentationErrors ¶

Many IndentationError exceptions now have more context regarding what kind of block was expecting an indentation, including the location of the statement:

>>> 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?

(Contributed by Pablo Galindo in 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?

(Contributed by Pablo Galindo in 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: Precise line numbers for debugging and other tools ¶

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: Structural Pattern Matching ¶

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.

Syntax and operations ¶

The generic syntax of pattern matching is:

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

A match statement takes an expression and compares its value to successive patterns given as one or more case blocks. Specifically, pattern matching operates by:

using data with type and shape (the subject )
evaluating the subject 在 match 语句
comparing the subject with each pattern in a case statement from top to bottom until a match is confirmed.
executing the action associated with the pattern of the confirmed match
If an exact match is not confirmed, the last case, a wildcard _ , if provided, will be used as the matching case. If an exact match is not confirmed and a wildcard case does not exist, the entire match block is a no-op.

Declarative approach ¶

Readers may be aware of pattern matching through the simple example of matching a subject (data object) to a literal (pattern) with the switch statement found in C, Java or JavaScript (and many other languages). Often the switch statement is used for comparison of an object/expression with case statements containing literals.

More powerful examples of pattern matching can be found in languages such as Scala and Elixir. With structural pattern matching, the approach is “declarative” and explicitly states the conditions (the patterns) for data to match.

While an “imperative” series of instructions using nested “if” statements could be used to accomplish something similar to structural pattern matching, it is less clear than the “declarative” approach. Instead the “declarative” approach states the conditions to meet for a match and is more readable through its explicit patterns. While structural pattern matching can be used in its simplest form comparing a variable to a literal in a case statement, its true value for Python lies in its handling of the subject’s type and shape.

Simple pattern: match to a literal ¶

Let’s look at this example as pattern matching in its simplest form: a value, the subject, being matched to several literals, the patterns. In the example below, status is the subject of the match statement. The patterns are each of the case statements, where literals represent request status codes. The associated action to the case is executed after a match:

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"

If the above function is passed a status of 418, “I’m a teapot” is returned. If the above function is passed a status of 500, the case statement with _ will match as a wildcard, and “Something’s wrong with the internet” is returned. Note the last block: the variable name, _ , acts as a wildcard and insures the subject will always match. The use of _ is optional.

You can combine several literals in a single pattern using | (“or”):

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

Behavior without the wildcard ¶

If we modify the above example by removing the last case block, the example becomes:

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

Without the use of _ in a case statement, a match may not exist. If no match exists, the behavior is a no-op. For example, if status of 500 is passed, a no-op occurs.

Patterns with a literal and variable ¶

Patterns can look like unpacking assignments, and a pattern may be used to bind variables. In this example, a data point can be unpacked to its x-coordinate and y-coordinate:

# point is an (x, y) tuple
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")

The first pattern has two literals, (0, 0) , and may be thought of as an extension of the literal pattern shown above. The next two patterns combine a literal and a variable, and the variable binds a value from the subject ( point ). The fourth pattern captures two values, which makes it conceptually similar to the unpacking assignment (x, y) = point .

Patterns and classes ¶

If you are using classes to structure your data, you can use as a pattern the class name followed by an argument list resembling a constructor. This pattern has the ability to capture class attributes into variables:

class Point:
    x: int
    y: int
def location(point):
    match point:
        case Point(x=0, y=0):
            print("Origin is the point's location.")
        case Point(x=0, y=y):
            print(f"Y={y} and the point is on the y-axis.")
        case Point(x=x, y=0):
            print(f"X={x} and the point is on the x-axis.")
        case Point():
            print("The point is located somewhere else on the plane.")
        case _:
            print("Not a point")

Patterns with positional parameters ¶

You can use positional parameters with some builtin classes that provide an ordering for their attributes (e.g. dataclasses). You can also define a specific position for attributes in patterns by setting the __match_args__ special attribute in your classes. If it’s set to (“x”, “y”), the following patterns are all equivalent (and all bind the y 属性到 var variable):

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

Nested patterns ¶

Patterns can be arbitrarily nested. For example, if our data is a short list of points, it could be matched like this:

match points:
    case []:
        print("No points in the list.")
    case [Point(0, 0)]:
        print("The origin is the only point in the list.")
    case [Point(x, y)]:
        print(f"A single point {x}, {y} is in the list.")
    case [Point(0, y1), Point(0, y2)]:
        print(f"Two points on the Y axis at {y1}, {y2} are in the list.")
    case _:
        print("Something else is found in the list.")

Complex patterns and the wildcard ¶

To this point, the examples have used _ alone in the last case statement. A wildcard can be used in more complex patterns, such as ('error', code, _) 。例如：

match test_variable:
    case ('warning', code, 40):
        print("A warning has been received.")
    case ('error', code, _):
        print(f"An error {code} occurred.")

In the above case, test_variable will match for (‘error’, code, 100) and (‘error’, code, 800).

Guard ¶

We can add an if clause to a pattern, known as a “guard”. If the guard is false, match goes on to try the next case block. Note that value capture happens before the guard is evaluated:

match point:
    case Point(x, y) if x == y:
        print(f"The point is located on the diagonal Y=X at {x}.")
    case Point(x, y):
        print(f"Point is not on the diagonal.")

Other Key Features ¶

Several other key features:

Like unpacking assignments, tuple and list patterns have exactly the same meaning and actually match arbitrary sequences. Technically, the subject must be a sequence. Therefore, an important exception is that patterns don’t match iterators. Also, to prevent a common mistake, sequence patterns don’t match strings.
Sequence patterns support wildcards: [x, y, *rest] and (x, y, *rest) work similar to wildcards in unpacking assignments. The name after * 还可以为 _ ，所以 (x, y, *_) matches a sequence of at least two items without binding the remaining items.
Mapping patterns: {"bandwidth": b, "latency": l} captures the "bandwidth" and "latency" values from a dict. Unlike sequence patterns, extra keys are ignored. A wildcard **rest is also supported. (But **_ would be redundant, so is not allowed.)
Subpatterns may be captured using the as 关键词：
```
case (Point(x1, y1), Point(x2, y2) as p2): ...
											
```
This binds x1, y1, x2, y2 like you would expect without the as clause, and p2 to the entire second item of the subject.
Most literals are compared by equality. However, the singletons True , False and None are compared by identity.

Named constants may be used in patterns. These named constants must be dotted names to prevent the constant from being interpreted as a capture variable:

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 :(")

For the full specification see PEP 634 . Motivation and rationale are in PEP 635 , and a longer tutorial is in PEP 636 .

可选 `EncodingWarning` and `encoding="locale"` option ¶

默认编码对于 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 选项和 PYTHONWARNDEFAULTENCODING are added to enable the warning.

见文本编码了解更多信息。

New Features Related to Type Hints ¶

This section covers major changes affecting PEP 484 type hints and the typing 模块。

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

见 Union 类型 and PEP 604 了解更多细节。

(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 模块。

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 .

见 typing.Callable , typing.ParamSpec , typing.Concatenate , typing.ParamSpecArgs , typing.ParamSpecKwargs ，和 PEP 612 了解更多细节。

(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

见 PEP 613 了解更多细节。

(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.)

其它语言变化 ¶

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 ： 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 )。
若 object.__ipow__() 返回 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__ ) 且拥有新的 __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 注解最佳实践 . (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 类型和 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 )。

新模块 ¶

None.

改进模块 ¶

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() 方法为 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 ¶

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

bdb ¶

添加 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 ¶

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

collections.abc ¶

The __args__ 的 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 ¶

添加 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 )。

添加 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() ，和 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 )。

dataclasses ¶

slots ¶

添加 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

这里， 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 )。

encodings ¶

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 )。

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

fileinput ¶

添加 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 ¶

添加 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 and idlelib ¶

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 ，和 _ 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.

添加 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 )。

添加 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 注解最佳实践 . Relatedly, inspect.signature() , inspect.Signature.from_callable() ，和 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 ¶

添加 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 ¶

添加 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 )。

添加 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 )。

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

os.path ¶

os.path.realpath() 现在接受 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 )。

添加 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 )。

platform ¶

添加 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 ¶

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

pyclbr ¶

添加 end_lineno 属性到 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 ¶

添加 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 现在是别名化的 TimeoutError . (Contributed by Christian Heimes in bpo-42413 )。

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

添加 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 ，和 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.

添加 timeout 参数用于 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/handle() , enable_load_extension() ，和 load_extension() . (Contributed by Erlend E. Aasland in bpo-43762 )。

sys ¶

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

添加 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 ¶

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

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

类型 ¶

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 New Features Related to Type Hints .

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

Literal now de-duplicates parameters.
Equality comparisons between Literal objects are now order independent.
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.

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'

(Contributed by Yurii Karabas in bpo-42345 )。

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

子类化的 typing.Protocol which only have data variables declared will now raise a TypeError when checked with isinstance unless they are decorated with 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 。(见 gh-88048 )

xml ¶

添加 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() ，和 zipimport.zipimporter.exec_module() . (Contributed by Brett Cannon in bpo-42131 )。

添加 invalidate_caches() method. (Contributed by Desmond Cheong in bpo-14678 )。

优化 ¶

构造函数 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 )。

弃用 ¶

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 )， __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 。使用 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() )，和 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 ，和 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() ，和 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 )。
下列 threading methods are now deprecated:
- 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 )。
下列 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 ，和 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 ，和 PROTOCOL_TLS 弃用代之 PROTOCOL_TLS_CLIENT and PROTOCOL_TLS_SERVER
- wrap_socket() 被替换通过 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 )。

移除 ¶

Removed special methods __int__ , __float__ , __floordiv__ , __mod__ , __divmod__ , __rfloordiv__ , __rmod__ and __rdivmod__ 的 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 及其 error() implementation was already removed in Python 3.5. (Contributed by Berker Peksag in bpo-31844 )。
移除 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 )。
移除 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.
移除 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 )。
移除 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 集合抽象基类从 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 。见 Python API 变化 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 ¶

This section lists previously described changes and other bugfixes that may require changes to your code.

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 变化 ¶

The etype parameters of the format_exception() , format_exception_only() ，和 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() 现在引发 OverflowError 而不是 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)
```
若 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() 代替。

(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 变化 ¶

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:
- 调用 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() 代替。

CPython 字节码变化 ¶

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 )。

构建变化 ¶

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 )。
添加 --disable-test-modules 选项到 configure script: don’t build nor install test modules. (Contributed by Xavier de Gaye, Thomas Petazzoni and Peixing Xin in bpo-27640 )。
添加 --with-wheel-pkg-dir=PATH option 到 ./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 包。

(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 )。
添加 --with-openssl-rpath 选项到 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 变化 ¶

PEP 652: Maintaining the Stable ABI ¶

The Stable ABI (Application Binary Interface) for extension modules or embedding Python is now explicitly defined. C API 稳定性 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 )。

新特征 ¶

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 )。
添加 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 )。
添加 PyUnicode_AsUTF8AndSize() to the limited C API. (Contributed by Alex Gaynor in bpo-41784 )。
添加 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 )。
添加 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 )。
添加 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 )。
添加 Py_Is(x, y) function to test if the x 对象是 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 模块。
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# 。见解析自变量和构建值 and PEP 353 . (Contributed by Victor Stinner in bpo-40943 )。
由于 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 )。
调用 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 )。
私有 _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 初始化配置 API to get the Python 路径配置 . (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 ，和 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 ；见包括文件 . If they have been included directly, consider including Python.h instead. (Contributed by Nicholas Sim in bpo-35134 )。
使用 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 )。

弃用 ¶

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 )。

移除 ¶

移除 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()
移除 PyUnicode_GetMax() . Please migrate to new ( PEP 393 ) APIs. (Contributed by Inada Naoki in bpo-41103 )。
移除 PyLong_FromUnicode() . Please migrate to PyLong_FromUnicodeObject() . (Contributed by Inada Naoki in bpo-41103 )。
移除 PyUnicode_AsUnicodeCopy() 。请使用 PyUnicode_AsUCS4Copy() or PyUnicode_AsWideCharString() (Contributed by Inada Naoki in bpo-41103 )。
移除 _Py_CheckRecursionLimit variable: it has been replaced by ceval.recursion_limit 的 PyInterpreterState structure. (Contributed by Victor Stinner in bpo-41834 )。
Removed undocumented macros Py_ALLOW_RECURSION and Py_END_ALLOW_RECURSION 和 recursion_critical 字段的 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 )。
移除 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 )。
移除 ast.h , asdl.h ，和 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 API。见整数字符串转换长度局限性 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 ，和 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 )。

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