# What\'s New In Python 3.10 Editor : Pablo Galindo Salgado > \* Anyone can add text to this document. Do not spend very much time on the wording of your changes, because your text will probably get rewritten to some degree. > > \* The maintainer will go through Misc/NEWS periodically and add changes; it\'s therefore more important to add your changes to Misc/NEWS than to this file. > > \* This is not a complete list of every single change; completeness is the purpose of Misc/NEWS. Some changes I consider too small or esoteric to include. If such a change is added to the text, I\'ll just remove it. (This is another reason you shouldn\'t spend too much time on writing your addition.) > > \* If you want to draw your new text to the attention of the maintainer, add \'XXX\' to the beginning of the paragraph or section. > > \* It\'s OK to just add a fragmentary note about a change. For example: \"XXX Describe the transmogrify() function added to the socket module.\" The maintainer will research the change and write the necessary text. > > \* You can comment out your additions if you like, but it\'s not necessary (especially when a final release is some months away). > > \* Credit the author of a patch or bugfix. Just the name is sufficient; the e-mail address isn\'t necessary. > > - It\'s helpful to add the bug/patch number as a comment: > > XXX Describe the transmogrify() function added to the socket module. (Contributed by P.Y. Developer in `12345`{.interpreted-text role="issue"}.) > > This saves the maintainer the effort of going through the git log when researching a change. 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 `{.interpreted-text role="ref"}. ## Summary \-- Release highlights New syntax features: - `634`{.interpreted-text role="pep"}, Structural Pattern Matching: Specification - `635`{.interpreted-text role="pep"}, Structural Pattern Matching: Motivation and Rationale - `636`{.interpreted-text role="pep"}, Structural Pattern Matching: Tutorial - `12782`{.interpreted-text role="issue"}, Parenthesized context managers are now officially allowed. New features in the standard library: - `618`{.interpreted-text role="pep"}, Add Optional Length-Checking To zip. Interpreter improvements: - `626`{.interpreted-text role="pep"}, Precise line numbers for debugging and other tools. New typing features: - `604`{.interpreted-text role="pep"}, Allow writing union types as X \| Y - `612`{.interpreted-text role="pep"}, Parameter Specification Variables - `613`{.interpreted-text role="pep"}, Explicit Type Aliases - `647`{.interpreted-text role="pep"}, User-Defined Type Guards Important deprecations, removals or restrictions: - `644`{.interpreted-text role="pep"}, Require OpenSSL 1.1.1 or newer - `632`{.interpreted-text role="pep"}, Deprecate distutils module. - `623`{.interpreted-text role="pep"}, Deprecate and prepare for the removal of the wstr member in PyUnicodeObject. - `624`{.interpreted-text role="pep"}, Remove Py_UNICODE encoder APIs - `597`{.interpreted-text role="pep"}, Add optional EncodingWarning ## New Features ### Parenthesized context managers {#whatsnew310-pep563} 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: ``` python 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: ``` python with ( CtxManager1() as example1, CtxManager2() as example2, CtxManager3() as example3, ): ... ``` This new syntax uses the non LL(1) capacities of the new parser. Check `617`{.interpreted-text role="pep"} for more details. (Contributed by Guido van Rossum, Pablo Galindo and Lysandros Nikolaou in `12782`{.interpreted-text role="issue"} and `40334`{.interpreted-text role="issue"}.) ### 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 \'{\'): ``` python 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: ``` python File "example.py", line 3 some_other_code = foo() ^ SyntaxError: invalid syntax ``` but in Python 3.10 a more informative error is emitted: ``` python 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 `42864`{.interpreted-text role="issue"} and Batuhan Taskaya in `40176`{.interpreted-text role="issue"}.) `SyntaxError`{.interpreted-text role="exc"} 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): ``` python >>> foo(x, z for z in range(10), t, w) File "", 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: ``` python >>> foo(x, z for z in range(10), t, w) File "", 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 `43914`{.interpreted-text role="issue"}. A considerable amount of new specialized messages for `SyntaxError`{.interpreted-text role="exc"} exceptions have been incorporated. Some of the most notable ones are as follows: - Missing `:` before blocks: ``` python >>> if rocket.position > event_horizon File "", line 1 if rocket.position > event_horizon ^ SyntaxError: expected ':' ``` (Contributed by Pablo Galindo in `42997`{.interpreted-text role="issue"}.) - Unparenthesised tuples in comprehensions targets: ``` python >>> {x,y for x,y in zip('abcd', '1234')} File "", 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 `43017`{.interpreted-text role="issue"}.) - Missing commas in collection literals and between expressions: ``` python >>> items = { ... x: 1, ... y: 2 ... z: 3, File "", line 3 y: 2 ^ SyntaxError: invalid syntax. Perhaps you forgot a comma? ``` (Contributed by Pablo Galindo in `43822`{.interpreted-text role="issue"}.) - Multiple Exception types without parentheses: ``` python >>> try: ... build_dyson_sphere() ... except NotEnoughScienceError, NotEnoughResourcesError: File "", line 3 except NotEnoughScienceError, NotEnoughResourcesError: ^ SyntaxError: multiple exception types must be parenthesized ``` (Contributed by Pablo Galindo in `43149`{.interpreted-text role="issue"}.) - Missing `:` and values in dictionary literals: ``` python >>> values = { ... x: 1, ... y: 2, ... z: ... } File "", line 4 z: ^ SyntaxError: expression expected after dictionary key and ':' >>> values = {x:1, y:2, z w:3} File "", line 1 values = {x:1, y:2, z w:3} ^ SyntaxError: ':' expected after dictionary key ``` (Contributed by Pablo Galindo in `43823`{.interpreted-text role="issue"}.) - `try` blocks without `except` or `finally` blocks: ``` python >>> try: ... x = 2 ... something = 3 File "", line 3 something = 3 ^^^^^^^^^ SyntaxError: expected 'except' or 'finally' block ``` (Contributed by Pablo Galindo in `44305`{.interpreted-text role="issue"}.) - Usage of `=` instead of `==` in comparisons: ``` python >>> if rocket.position = event_horizon: File "", line 1 if rocket.position = event_horizon: ^ SyntaxError: cannot assign to attribute here. Maybe you meant '==' instead of '='? ``` (Contributed by Pablo Galindo in `43797`{.interpreted-text role="issue"}.) - Usage of `*` in f-strings: ``` python >>> f"Black holes {*all_black_holes} and revelations" File "", line 1 (*all_black_holes) ^ SyntaxError: f-string: cannot use starred expression here ``` (Contributed by Pablo Galindo in `41064`{.interpreted-text role="issue"}.) #### IndentationErrors Many `IndentationError`{.interpreted-text role="exc"} exceptions now have more context regarding what kind of block was expecting an indentation, including the location of the statement: ``` python >>> def foo(): ... if lel: ... x = 2 File "", line 3 x = 2 ^ IndentationError: expected an indented block after 'if' statement in line 2 ``` #### AttributeErrors When printing `AttributeError`{.interpreted-text role="exc"}, `!PyErr_Display`{.interpreted-text role="c:func"} will offer suggestions of similar attribute names in the object that the exception was raised from: ``` python >>> collections.namedtoplo Traceback (most recent call last): File "", line 1, in AttributeError: module 'collections' has no attribute 'namedtoplo'. Did you mean: namedtuple? ``` (Contributed by Pablo Galindo in `38530`{.interpreted-text role="issue"}.) :::: warning ::: title Warning ::: Notice this won\'t work if `!PyErr_Display`{.interpreted-text role="c:func"} 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`{.interpreted-text role="exc"} raised by the interpreter, `!PyErr_Display`{.interpreted-text role="c:func"} will offer suggestions of similar variable names in the function that the exception was raised from: ``` python >>> schwarzschild_black_hole = None >>> schwarschild_black_hole Traceback (most recent call last): File "", line 1, in NameError: name 'schwarschild_black_hole' is not defined. Did you mean: schwarzschild_black_hole? ``` (Contributed by Pablo Galindo in `38530`{.interpreted-text role="issue"}.) :::: warning ::: title Warning ::: Notice this won\'t work if `!PyErr_Display`{.interpreted-text role="c:func"} 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 `~frame.f_lineno`{.interpreted-text role="attr"} attribute of frame objects will always contain the expected line number. The `~codeobject.co_lnotab`{.interpreted-text role="attr"} attribute of `code objects `{.interpreted-text role="ref"} is deprecated and will be removed in 3.12. Code that needs to convert from offset to line number should use the new `~codeobject.co_lines`{.interpreted-text role="meth"} 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 : case : case : case _: 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: 1. using data with type and shape (the `subject`) 2. evaluating the `subject` in the `match` statement 3. comparing the subject with each pattern in a `case` statement from top to bottom until a match is confirmed. 4. executing the action associated with the pattern of the confirmed match 5. 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 instance attributes into variables: 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("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` attribute to the `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, _)`. For example: 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 `*` may also be `_`, so `(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` keyword: 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 `634`{.interpreted-text role="pep"}. Motivation and rationale are in `635`{.interpreted-text role="pep"}, and a longer tutorial is in `636`{.interpreted-text role="pep"}. ### Optional `EncodingWarning` and `encoding="locale"` option {#whatsnew310-pep597} The default encoding of `~io.TextIOWrapper`{.interpreted-text role="class"} and `open`{.interpreted-text role="func"} 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 `{.interpreted-text role="data"} is true and locale-specific default encoding is used. `-X warn_default_encoding` option and `PYTHONWARNDEFAULTENCODING`{.interpreted-text role="envvar"} are added to enable the warning. See `io-text-encoding`{.interpreted-text role="ref"} for more information. ## New Features Related to Type Hints {#new-feat-related-type-hints} This section covers major changes affecting `484`{.interpreted-text role="pep"} type hints and the `typing`{.interpreted-text role="mod"} 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`{.interpreted-text role="class"}, especially in type hints. In previous versions of Python, to apply a type hint for functions accepting arguments of multiple types, `typing.Union`{.interpreted-text role="class"} 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`{.interpreted-text role="func"} and `issubclass`{.interpreted-text role="func"}: >>> isinstance(1, int | str) True See `types-union`{.interpreted-text role="ref"} and `604`{.interpreted-text role="pep"} for more details. (Contributed by Maggie Moss and Philippe Prados in `41428`{.interpreted-text role="issue"}, with additions by Yurii Karabas and Serhiy Storchaka in `44490`{.interpreted-text role="issue"}.) ### PEP 612: Parameter Specification Variables Two new options to improve the information provided to static type checkers for `484`{.interpreted-text role="pep"}\'s `Callable` have been added to the `typing`{.interpreted-text role="mod"} 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`{.interpreted-text role="class"}. 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`{.interpreted-text role="class"}. See `typing.Callable`{.interpreted-text role="class"}, `typing.ParamSpec`{.interpreted-text role="class"}, `typing.Concatenate`{.interpreted-text role="class"}, `typing.ParamSpecArgs`{.interpreted-text role="class"}, `typing.ParamSpecKwargs`{.interpreted-text role="class"}, and `612`{.interpreted-text role="pep"} for more details. (Contributed by Ken Jin in `41559`{.interpreted-text role="issue"}, with minor enhancements by Jelle Zijlstra in `43783`{.interpreted-text role="issue"}. PEP written by Mark Mendoza.) ### PEP 613: TypeAlias `484`{.interpreted-text role="pep"} 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`{.interpreted-text role="mod"} module has a special value `~typing.TypeAlias`{.interpreted-text role="data"} which lets you declare type aliases more explicitly: StrCache: TypeAlias = 'Cache[str]' # a type alias LOG_PREFIX = 'LOG[DEBUG]' # a module constant See `613`{.interpreted-text role="pep"} for more details. (Contributed by Mikhail Golubev in `41923`{.interpreted-text role="issue"}.) ### PEP 647: User-Defined Type Guards `~typing.TypeGuard`{.interpreted-text role="data"} has been added to the `typing`{.interpreted-text role="mod"} module to annotate type guard functions and improve information provided to static type checkers during type narrowing. For more information, please see `~typing.TypeGuard`{.interpreted-text role="data"}\'s documentation, and `647`{.interpreted-text role="pep"}. (Contributed by Ken Jin and Guido van Rossum in `43766`{.interpreted-text role="issue"}. PEP written by Eric Traut.) ## Other Language Changes - The `int`{.interpreted-text role="class"} type has a new method `int.bit_count`{.interpreted-text role="meth"}, returning the number of ones in the binary expansion of a given integer, also known as the population count. (Contributed by Niklas Fiekas in `29882`{.interpreted-text role="issue"}.) - The views returned by `dict.keys`{.interpreted-text role="meth"}, `dict.values`{.interpreted-text role="meth"} and `dict.items`{.interpreted-text role="meth"} now all have a `mapping` attribute that gives a `types.MappingProxyType`{.interpreted-text role="class"} object wrapping the original dictionary. (Contributed by Dennis Sweeney in `40890`{.interpreted-text role="issue"}.) - `618`{.interpreted-text role="pep"}: The `zip`{.interpreted-text role="func"} 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.Decimal`{.interpreted-text role="class"}s, `~fractions.Fraction`{.interpreted-text role="class"}s and other objects that can be converted to integers only with a loss (e.g. that have the `~object.__int__`{.interpreted-text role="meth"} method but do not have the `~object.__index__`{.interpreted-text role="meth"} method). (Contributed by Serhiy Storchaka in `37999`{.interpreted-text role="issue"}.) - If `object.__ipow__`{.interpreted-text role="func"} returns `NotImplemented`{.interpreted-text role="data"}, the operator will correctly fall back to `object.__pow__`{.interpreted-text role="func"} and `object.__rpow__`{.interpreted-text role="func"} as expected. (Contributed by Alex Shkop in `38302`{.interpreted-text role="issue"}.) - 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 `42990`{.interpreted-text role="issue"}.) - Two new builtin functions \-- `aiter`{.interpreted-text role="func"} and `anext`{.interpreted-text role="func"} have been added to provide asynchronous counterparts to `iter`{.interpreted-text role="func"} and `next`{.interpreted-text role="func"}, respectively. (Contributed by Joshua Bronson, Daniel Pope, and Justin Wang in `31861`{.interpreted-text role="issue"}.) - Static methods (`staticmethod`{.interpreted-text role="deco"}) and class methods (`classmethod`{.interpreted-text role="deco"}) 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 `43682`{.interpreted-text role="issue"}.) - Annotations for complex targets (everything beside `simple name` targets defined by `526`{.interpreted-text role="pep"}) no longer cause any runtime effects with `from __future__ import annotations`. (Contributed by Batuhan Taskaya in `42737`{.interpreted-text role="issue"}.) - 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 `annotations-howto`{.interpreted-text role="ref"}. (Contributed by Larry Hastings in `43901`{.interpreted-text role="issue"}.) - 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 `42725`{.interpreted-text role="issue"}.) - 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 `42725`{.interpreted-text role="issue"}.) - Hashes of NaN values of both `float`{.interpreted-text role="class"} type and `decimal.Decimal`{.interpreted-text role="class"} 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 `43475`{.interpreted-text role="issue"}.) - A `SyntaxError`{.interpreted-text role="exc"} (instead of a `NameError`{.interpreted-text role="exc"}) will be raised when deleting the `__debug__`{.interpreted-text role="const"} constant. (Contributed by Donghee Na in `45000`{.interpreted-text role="issue"}.) - `SyntaxError`{.interpreted-text role="exc"} exceptions now have `end_lineno` and `end_offset` attributes. They will be `None` if not determined. (Contributed by Pablo Galindo in `43914`{.interpreted-text role="issue"}.) ## New Modules - None. ## Improved Modules ### asyncio Add missing `~asyncio.loop.connect_accepted_socket`{.interpreted-text role="meth"} method. (Contributed by Alex Grönholm in `41332`{.interpreted-text role="issue"}.) ### 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 `9694`{.interpreted-text role="issue"}.) ### array The `~array.array.index`{.interpreted-text role="meth"} method of `array.array`{.interpreted-text role="class"} now has optional *start* and *stop* parameters. (Contributed by Anders Lorentsen and Zackery Spytz in `31956`{.interpreted-text role="issue"}.) ### asynchat, asyncore, smtpd These modules have been marked as deprecated in their module documentation since Python 3.6. An import-time `DeprecationWarning`{.interpreted-text role="class"} has now been added to all three of these modules. ### base64 Add `base64.b32hexencode`{.interpreted-text role="func"} and `base64.b32hexdecode`{.interpreted-text role="func"} to support the Base32 Encoding with Extended Hex Alphabet. ### bdb Add `!clearBreakpoints`{.interpreted-text role="meth"} to reset all set breakpoints. (Contributed by Irit Katriel in `24160`{.interpreted-text role="issue"}.) ### bisect Added the possibility of providing a *key* function to the APIs in the `bisect`{.interpreted-text role="mod"} module. (Contributed by Raymond Hettinger in `4356`{.interpreted-text role="issue"}.) ### codecs Add a `codecs.unregister`{.interpreted-text role="func"} function to unregister a codec search function. (Contributed by Hai Shi in `41842`{.interpreted-text role="issue"}.) ### collections.abc The `__args__` of the `parameterized generic `{.interpreted-text role="ref"} for `collections.abc.Callable`{.interpreted-text role="class"} are now consistent with `typing.Callable`{.interpreted-text role="data"}. `collections.abc.Callable`{.interpreted-text role="class"} generic now flattens type parameters, similar to what `typing.Callable`{.interpreted-text role="data"} 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`{.interpreted-text role="class"} can now be subclassed, and a subclass will be returned when subscripting the `collections.abc.Callable`{.interpreted-text role="class"} type. Note that a `TypeError`{.interpreted-text role="exc"} may be raised for invalid forms of parameterizing `collections.abc.Callable`{.interpreted-text role="class"} which may have passed silently in Python 3.9. (Contributed by Ken Jin in `42195`{.interpreted-text role="issue"}.) ### contextlib Add a `contextlib.aclosing`{.interpreted-text role="func"} context manager to safely close async generators and objects representing asynchronously released resources. (Contributed by Joongi Kim and John Belmonte in `41229`{.interpreted-text role="issue"}.) Add asynchronous context manager support to `contextlib.nullcontext`{.interpreted-text role="func"}. (Contributed by Tom Gringauz in `41543`{.interpreted-text role="issue"}.) Add `~contextlib.AsyncContextDecorator`{.interpreted-text role="class"}, 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`{.interpreted-text role="func"}, `curses.init_color`{.interpreted-text role="func"}, `curses.init_pair`{.interpreted-text role="func"}, and `curses.pair_content`{.interpreted-text role="func"}. A new function, `curses.has_extended_color_support`{.interpreted-text role="func"}, indicates whether extended color support is provided by the underlying ncurses library. (Contributed by Jeffrey Kintscher and Hans Petter Jansson in `36982`{.interpreted-text role="issue"}.) The `BUTTON5_*` constants are now exposed in the `curses`{.interpreted-text role="mod"} module if they are provided by the underlying curses library. (Contributed by Zackery Spytz in `39273`{.interpreted-text role="issue"}.) ### dataclasses #### \_\_slots\_\_ Added `slots` parameter in `dataclasses.dataclass`{.interpreted-text role="func"} decorator. (Contributed by Yurii Karabas in `42269`{.interpreted-text role="issue"}) #### 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: ``` python 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: ``` python 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: ``` python 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 `43532`{.interpreted-text role="issue"}.) ### distutils {#distutils-deprecated} 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`{.interpreted-text role="mod"}, `shutil`{.interpreted-text role="mod"}, `subprocess`{.interpreted-text role="mod"} or `sysconfig`{.interpreted-text role="mod"}). 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 `632`{.interpreted-text role="pep"} 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 `42802`{.interpreted-text role="issue"}.) ### doctest When a module does not define `__loader__`, fall back to `__spec__.loader`. (Contributed by Brett Cannon in `42133`{.interpreted-text role="issue"}.) ### encodings `encodings.normalize_encoding`{.interpreted-text role="func"} now ignores non-ASCII characters. (Contributed by Hai Shi in `39337`{.interpreted-text role="issue"}.) ### enum `~enum.Enum`{.interpreted-text role="class"} `~object.__repr__`{.interpreted-text role="func"} now returns `enum_name.member_name` and `~object.__str__`{.interpreted-text role="func"} now returns `member_name`. Stdlib enums available as module constants have a `repr`{.interpreted-text role="func"} of `module_name.member_name`. (Contributed by Ethan Furman in `40066`{.interpreted-text role="issue"}.) Add `enum.StrEnum`{.interpreted-text role="class"} for enums where all members are strings. (Contributed by Ethan Furman in `41816`{.interpreted-text role="issue"}.) ### fileinput Add *encoding* and *errors* parameters in `fileinput.input`{.interpreted-text role="func"} and `fileinput.FileInput`{.interpreted-text role="class"}. (Contributed by Inada Naoki in `43712`{.interpreted-text role="issue"}.) `fileinput.hook_compressed`{.interpreted-text role="func"} now returns `~io.TextIOWrapper`{.interpreted-text role="class"} object when *mode* is \"r\" and file is compressed, like uncompressed files. (Contributed by Inada Naoki in `5758`{.interpreted-text role="issue"}.) ### faulthandler The `faulthandler`{.interpreted-text role="mod"} module now detects if a fatal error occurs during a garbage collector collection. (Contributed by Victor Stinner in `44466`{.interpreted-text role="issue"}.) ### gc Add audit hooks for `gc.get_objects`{.interpreted-text role="func"}, `gc.get_referrers`{.interpreted-text role="func"} and `gc.get_referents`{.interpreted-text role="func"}. (Contributed by Pablo Galindo in `43439`{.interpreted-text role="issue"}.) ### glob Add the *root_dir* and *dir_fd* parameters in `~glob.glob`{.interpreted-text role="func"} and `~glob.iglob`{.interpreted-text role="func"} which allow to specify the root directory for searching. (Contributed by Serhiy Storchaka in `38144`{.interpreted-text role="issue"}.) ### hashlib The hashlib module requires OpenSSL 1.1.1 or newer. (Contributed by Christian Heimes in `644`{.interpreted-text role="pep"} and `43669`{.interpreted-text role="issue"}.) The hashlib module has preliminary support for OpenSSL 3.0.0. (Contributed by Christian Heimes in `38820`{.interpreted-text role="issue"} and other issues.) The pure-Python fallback of `~hashlib.pbkdf2_hmac`{.interpreted-text role="func"} is deprecated. In the future PBKDF2-HMAC will only be available when Python has been built with OpenSSL support. (Contributed by Christian Heimes in `43880`{.interpreted-text role="issue"}.) ### hmac The hmac module now uses OpenSSL\'s HMAC implementation internally. (Contributed by Christian Heimes in `40645`{.interpreted-text role="issue"}.) ### IDLE and idlelib Make IDLE invoke `sys.excepthook`{.interpreted-text role="func"} (when started without \'-n\'). User hooks were previously ignored. (Contributed by Ken Hilton in `43008`{.interpreted-text role="issue"}.) 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 `40468`{.interpreted-text role="issue"}.) Move the indent space setting from the Font tab to the new Windows tab. (Contributed by Mark Roseman and Terry Jan Reedy in `33962`{.interpreted-text role="issue"}.) 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 `37903`{.interpreted-text role="issue"}.) 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 `37892`{.interpreted-text role="issue"}.) Highlight the new `soft keywords `{.interpreted-text role="ref"} `match`{.interpreted-text role="keyword"}, `case `{.interpreted-text role="keyword"}, and `_ `{.interpreted-text role="keyword"} 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 `44010`{.interpreted-text role="issue"}.) New in 3.10 maintenance releases. Apply syntax highlighting to `.pyi` files. (Contributed by Alex Waygood and Terry Jan Reedy in `45447`{.interpreted-text role="issue"}.) Include prompts when saving Shell with inputs and outputs. (Contributed by Terry Jan Reedy in `95191`{.interpreted-text role="gh"}.) ### importlib.metadata Feature parity with `importlib_metadata` 4.6 ([history](https://importlib-metadata.readthedocs.io/en/latest/history.html)). `importlib.metadata entry points `{.interpreted-text role="ref"} now provide a nicer experience for selecting entry points by group and name through a new `importlib.metadata.EntryPoints `{.interpreted-text role="ref"} class. See the Compatibility Note in the docs for more info on the deprecation and usage. Added `importlib.metadata.packages_distributions() `{.interpreted-text role="ref"} for resolving top-level Python modules and packages to their `importlib.metadata.Distribution `{.interpreted-text role="ref"}. ### inspect When a module does not define `__loader__`, fall back to `__spec__.loader`. (Contributed by Brett Cannon in `42133`{.interpreted-text role="issue"}.) Add `inspect.get_annotations`{.interpreted-text role="func"}, 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`{.interpreted-text role="func"} can also correctly un-stringize stringized annotations. `inspect.get_annotations`{.interpreted-text role="func"} 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 `annotations-howto`{.interpreted-text role="ref"}. Relatedly, `inspect.signature`{.interpreted-text role="func"}, `inspect.Signature.from_callable`{.interpreted-text role="func"}, and `!inspect.Signature.from_function`{.interpreted-text role="func"} now call `inspect.get_annotations`{.interpreted-text role="func"} to retrieve annotations. This means `inspect.signature`{.interpreted-text role="func"} and `inspect.Signature.from_callable`{.interpreted-text role="func"} can also now un-stringize stringized annotations. (Contributed by Larry Hastings in `43817`{.interpreted-text role="issue"}.) ### itertools Add `itertools.pairwise`{.interpreted-text role="func"}. (Contributed by Raymond Hettinger in `38200`{.interpreted-text role="issue"}.) ### linecache When a module does not define `__loader__`, fall back to `__spec__.loader`. (Contributed by Brett Cannon in `42133`{.interpreted-text role="issue"}.) ### os Add `os.cpu_count`{.interpreted-text role="func"} support for VxWorks RTOS. (Contributed by Peixing Xin in `41440`{.interpreted-text role="issue"}.) Add a new function `os.eventfd`{.interpreted-text role="func"} and related helpers to wrap the `eventfd2` syscall on Linux. (Contributed by Christian Heimes in `41001`{.interpreted-text role="issue"}.) Add `os.splice`{.interpreted-text role="func"} 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 `41625`{.interpreted-text role="issue"}.) Add `~os.O_EVTONLY`{.interpreted-text role="const"}, `~os.O_FSYNC`{.interpreted-text role="const"}, `~os.O_SYMLINK`{.interpreted-text role="const"} and `~os.O_NOFOLLOW_ANY`{.interpreted-text role="const"} for macOS. (Contributed by Donghee Na in `43106`{.interpreted-text role="issue"}.) ### os.path `os.path.realpath`{.interpreted-text role="func"} now accepts a *strict* keyword-only argument. When set to `True`, `OSError`{.interpreted-text role="exc"} is raised if a path doesn\'t exist or a symlink loop is encountered. (Contributed by Barney Gale in `43757`{.interpreted-text role="issue"}.) ### pathlib Add slice support to `PurePath.parents `{.interpreted-text role="attr"}. (Contributed by Joshua Cannon in `35498`{.interpreted-text role="issue"}.) Add negative indexing support to `PurePath.parents `{.interpreted-text role="attr"}. (Contributed by Yaroslav Pankovych in `21041`{.interpreted-text role="issue"}.) Add `Path.hardlink_to `{.interpreted-text role="meth"} method that supersedes `!link_to`{.interpreted-text role="meth"}. The new method has the same argument order as `~pathlib.Path.symlink_to`{.interpreted-text role="meth"}. (Contributed by Barney Gale in `39950`{.interpreted-text role="issue"}.) `pathlib.Path.stat`{.interpreted-text role="meth"} and `~pathlib.Path.chmod`{.interpreted-text role="meth"} now accept a *follow_symlinks* keyword-only argument for consistency with corresponding functions in the `os`{.interpreted-text role="mod"} module. (Contributed by Barney Gale in `39906`{.interpreted-text role="issue"}.) ### platform Add `platform.freedesktop_os_release`{.interpreted-text role="func"} to retrieve operation system identification from [freedesktop.org os-release](https://www.freedesktop.org/software/systemd/man/os-release.html) standard file. (Contributed by Christian Heimes in `28468`{.interpreted-text role="issue"}.) ### pprint `pprint.pprint`{.interpreted-text role="func"} now accepts a new `underscore_numbers` keyword argument. (Contributed by sblondon in `42914`{.interpreted-text role="issue"}.) `pprint`{.interpreted-text role="mod"} can now pretty-print `dataclasses.dataclass`{.interpreted-text role="class"} instances. (Contributed by Lewis Gaul in `43080`{.interpreted-text role="issue"}.) ### py_compile Add `--quiet` option to command-line interface of `py_compile`{.interpreted-text role="mod"}. (Contributed by Gregory Schevchenko in `38731`{.interpreted-text role="issue"}.) ### pyclbr Add an `end_lineno` attribute to the `Function` and `Class` objects in the tree returned by `pyclbr.readmodule`{.interpreted-text role="func"} and `pyclbr.readmodule_ex`{.interpreted-text role="func"}. It matches the existing (start) `lineno`. (Contributed by Aviral Srivastava in `38307`{.interpreted-text role="issue"}.) ### shelve The `shelve`{.interpreted-text role="mod"} module now uses `pickle.DEFAULT_PROTOCOL`{.interpreted-text role="const"} by default instead of `pickle`{.interpreted-text role="mod"} protocol `3` when creating shelves. (Contributed by Zackery Spytz in `34204`{.interpreted-text role="issue"}.) ### statistics Add `~statistics.covariance`{.interpreted-text role="func"}, Pearson\'s `~statistics.correlation`{.interpreted-text role="func"}, and simple `~statistics.linear_regression`{.interpreted-text role="func"} functions. (Contributed by Tymoteusz Wołodźko in `38490`{.interpreted-text role="issue"}.) ### site When a module does not define `__loader__`, fall back to `__spec__.loader`. (Contributed by Brett Cannon in `42133`{.interpreted-text role="issue"}.) ### socket The exception `socket.timeout`{.interpreted-text role="exc"} is now an alias of `TimeoutError`{.interpreted-text role="exc"}. (Contributed by Christian Heimes in `42413`{.interpreted-text role="issue"}.) Add option to create MPTCP sockets with `IPPROTO_MPTCP` (Contributed by Rui Cunha in `43571`{.interpreted-text role="issue"}.) Add `IP_RECVTOS` option to receive the type of service (ToS) or DSCP/ECN fields (Contributed by Georg Sauthoff in `44077`{.interpreted-text role="issue"}.) ### ssl The ssl module requires OpenSSL 1.1.1 or newer. (Contributed by Christian Heimes in `644`{.interpreted-text role="pep"} and `43669`{.interpreted-text role="issue"}.) The ssl module has preliminary support for OpenSSL 3.0.0 and new option `~ssl.OP_IGNORE_UNEXPECTED_EOF`{.interpreted-text role="const"}. (Contributed by Christian Heimes in `38820`{.interpreted-text role="issue"}, `43794`{.interpreted-text role="issue"}, `43788`{.interpreted-text role="issue"}, `43791`{.interpreted-text role="issue"}, `43799`{.interpreted-text role="issue"}, `43920`{.interpreted-text role="issue"}, `43789`{.interpreted-text role="issue"}, and `43811`{.interpreted-text role="issue"}.) Deprecated function and use of deprecated constants now result in a `DeprecationWarning`{.interpreted-text role="exc"}. `ssl.SSLContext.options`{.interpreted-text role="attr"} has `~ssl.OP_NO_SSLv2`{.interpreted-text role="data"} and `~ssl.OP_NO_SSLv3`{.interpreted-text role="data"} set by default and therefore cannot warn about setting the flag again. The `deprecation section `{.interpreted-text role="ref"} has a list of deprecated features. (Contributed by Christian Heimes in `43880`{.interpreted-text role="issue"}.) 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. `~ssl.SSLContext`{.interpreted-text role="class"} defaults to minimum protocol version TLS 1.2. Settings are based on Hynek Schlawack\'s research. (Contributed by Christian Heimes in `43998`{.interpreted-text role="issue"}.) 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`{.interpreted-text role="func"} function. (Contributed by Zackery Spytz in `31870`{.interpreted-text role="issue"}.) The ssl module uses heap-types and multi-phase initialization. (Contributed by Christian Heimes in `42333`{.interpreted-text role="issue"}.) A new verify flag `~ssl.VERIFY_X509_PARTIAL_CHAIN`{.interpreted-text role="const"} has been added. (Contributed by l0x in `40849`{.interpreted-text role="issue"}.) ### sqlite3 Add audit events for `~sqlite3.connect`{.interpreted-text role="func"}, `~sqlite3.Connection.enable_load_extension`{.interpreted-text role="meth"}, and `~sqlite3.Connection.load_extension`{.interpreted-text role="meth"}. (Contributed by Erlend E. Aasland in `43762`{.interpreted-text role="issue"}.) ### sys Add `sys.orig_argv`{.interpreted-text role="data"} attribute: the list of the original command line arguments passed to the Python executable. (Contributed by Victor Stinner in `23427`{.interpreted-text role="issue"}.) Add `sys.stdlib_module_names`{.interpreted-text role="data"}, containing the list of the standard library module names. (Contributed by Victor Stinner in `42955`{.interpreted-text role="issue"}.) ### [thread]{#thread} `_thread.interrupt_main`{.interpreted-text role="func"} now takes an optional signal number to simulate (the default is still `signal.SIGINT`{.interpreted-text role="const"}). (Contributed by Antoine Pitrou in `43356`{.interpreted-text role="issue"}.) ### threading Add `threading.gettrace`{.interpreted-text role="func"} and `threading.getprofile`{.interpreted-text role="func"} to retrieve the functions set by `threading.settrace`{.interpreted-text role="func"} and `threading.setprofile`{.interpreted-text role="func"} respectively. (Contributed by Mario Corchero in `42251`{.interpreted-text role="issue"}.) Add `threading.__excepthook__`{.interpreted-text role="data"} to allow retrieving the original value of `threading.excepthook`{.interpreted-text role="func"} in case it is set to a broken or a different value. (Contributed by Mario Corchero in `42308`{.interpreted-text role="issue"}.) ### traceback The `~traceback.format_exception`{.interpreted-text role="func"}, `~traceback.format_exception_only`{.interpreted-text role="func"}, and `~traceback.print_exception`{.interpreted-text role="func"} functions can now take an exception object as a positional-only argument. (Contributed by Zackery Spytz and Matthias Bussonnier in `26389`{.interpreted-text role="issue"}.) ### types Reintroduce the `types.EllipsisType`{.interpreted-text role="data"}, `types.NoneType`{.interpreted-text role="data"} and `types.NotImplementedType`{.interpreted-text role="data"} classes, providing a new set of types readily interpretable by type checkers. (Contributed by Bas van Beek in `41810`{.interpreted-text role="issue"}.) ### typing For major changes, see `new-feat-related-type-hints`{.interpreted-text role="ref"}. The behavior of `typing.Literal`{.interpreted-text role="class"} was changed to conform with `586`{.interpreted-text role="pep"} 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`{.interpreted-text role="exc"} exception during equality comparisons if any of their parameters are not `hashable`{.interpreted-text role="term"}. 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 "", line 1, in TypeError: unhashable type: 'set' (Contributed by Yurii Karabas in `42345`{.interpreted-text role="issue"}.) Add new function `typing.is_typeddict`{.interpreted-text role="func"} to introspect if an annotation is a `typing.TypedDict`{.interpreted-text role="class"}. (Contributed by Patrick Reader in `41792`{.interpreted-text role="issue"}.) 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`{.interpreted-text role="func"}. Previously, these checks passed silently. Users should decorate their subclasses with the `!runtime_checkable`{.interpreted-text role="func"} decorator if they want runtime protocols. (Contributed by Yurii Karabas in `38908`{.interpreted-text role="issue"}.) Importing from the `typing.io` and `typing.re` submodules will now emit `DeprecationWarning`{.interpreted-text role="exc"}. 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`{.interpreted-text role="mod"} instead. (Contributed by Sebastian Rittau in `38291`{.interpreted-text role="issue"}.) ### unittest Add new method `~unittest.TestCase.assertNoLogs`{.interpreted-text role="meth"} to complement the existing `~unittest.TestCase.assertLogs`{.interpreted-text role="meth"}. (Contributed by Kit Yan Choi in `39385`{.interpreted-text role="issue"}.) ### urllib.parse Python versions earlier than Python 3.10 allowed using both `;` and `&` as query parameter separators in `urllib.parse.parse_qs`{.interpreted-text role="func"} and `urllib.parse.parse_qsl`{.interpreted-text role="func"}. 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`{.interpreted-text role="func"} and `!cgi.parse_multipart`{.interpreted-text role="func"} 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 `42967`{.interpreted-text role="issue"}.) The presence of newline or tab characters in parts of a URL allows for some forms of attacks. Following the WHATWG specification that updates `3986`{.interpreted-text role="rfc"}, ASCII newline `\n`, `\r` and tab `\t` characters are stripped from the URL by the parser in `urllib.parse`{.interpreted-text role="mod"} preventing such attacks. The removal characters are controlled by a new module level variable `urllib.parse._UNSAFE_URL_BYTES_TO_REMOVE`. (See `88048`{.interpreted-text role="gh"}) ### xml Add a `~xml.sax.handler.LexicalHandler`{.interpreted-text role="class"} class to the `xml.sax.handler`{.interpreted-text role="mod"} module. (Contributed by Jonathan Gossage and Zackery Spytz in `35018`{.interpreted-text role="issue"}.) ### zipimport Add methods related to `451`{.interpreted-text role="pep"}: `~zipimport.zipimporter.find_spec`{.interpreted-text role="meth"}, `zipimport.zipimporter.create_module`{.interpreted-text role="meth"}, and `zipimport.zipimporter.exec_module`{.interpreted-text role="meth"}. (Contributed by Brett Cannon in `42131`{.interpreted-text role="issue"}.) Add `~zipimport.zipimporter.invalidate_caches`{.interpreted-text role="meth"} method. (Contributed by Desmond Cheong in `14678`{.interpreted-text role="issue"}.) ## Optimizations - Constructors `str`{.interpreted-text role="func"}, `bytes`{.interpreted-text role="func"} and `bytearray`{.interpreted-text role="func"} are now faster (around 30\--40% for small objects). (Contributed by Serhiy Storchaka in `41334`{.interpreted-text role="issue"}.) - The `runpy`{.interpreted-text role="mod"} 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 `41006`{.interpreted-text role="issue"} and `41718`{.interpreted-text role="issue"}.) - 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 `42093`{.interpreted-text role="issue"} and Guido van Rossum in `42927`{.interpreted-text role="issue"}, based on ideas implemented originally in PyPy and MicroPython.) - When building Python with `--enable-optimizations`{.interpreted-text role="option"} now `-fno-semantic-interposition` is added to both the compile and link line. This speeds builds of the Python interpreter created with `--enable-shared`{.interpreted-text role="option"} with `gcc` by up to 30%. See [this article](https://developers.redhat.com/blog/2020/06/25/red-hat-enterprise-linux-8-2-brings-faster-python-3-8-run-speeds/) for more details. (Contributed by Victor Stinner and Pablo Galindo in `38980`{.interpreted-text role="issue"}.) - Use a new output buffer management code for `bz2`{.interpreted-text role="mod"} / `lzma`{.interpreted-text role="mod"} / `zlib`{.interpreted-text role="mod"} 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 `41486`{.interpreted-text role="issue"}) - 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 `42202`{.interpreted-text role="issue"}.) - 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 `41972`{.interpreted-text role="issue"}) - 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 `43452`{.interpreted-text role="issue"}.) - The following built-in functions now support the faster `590`{.interpreted-text role="pep"} vectorcall calling convention: `map`{.interpreted-text role="func"}, `filter`{.interpreted-text role="func"}, `reversed`{.interpreted-text role="func"}, `bool`{.interpreted-text role="func"} and `float`{.interpreted-text role="func"}. (Contributed by Donghee Na and Jeroen Demeyer in `43575`{.interpreted-text role="issue"}, `43287`{.interpreted-text role="issue"}, `41922`{.interpreted-text role="issue"}, `41873`{.interpreted-text role="issue"} and `41870`{.interpreted-text role="issue"}.) - `~bz2.BZ2File`{.interpreted-text role="class"} performance is improved by removing internal `RLock`. This makes `!BZ2File`{.interpreted-text role="class"} thread unsafe in the face of multiple simultaneous readers or writers, just like its equivalent classes in `gzip`{.interpreted-text role="mod"} and `lzma`{.interpreted-text role="mod"} have always been. (Contributed by Inada Naoki in `43785`{.interpreted-text role="issue"}.) ## Deprecated {#whatsnew310-deprecated} - 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`{.interpreted-text role="keyword"}, `else`{.interpreted-text role="keyword"}, `for`{.interpreted-text role="keyword"}, `if`{.interpreted-text role="keyword"}, `in`{.interpreted-text role="keyword"}, `is`{.interpreted-text role="keyword"} and `or`{.interpreted-text role="keyword"}. In future releases it will be changed to syntax warning, and finally to syntax error. (Contributed by Serhiy Storchaka in `43833`{.interpreted-text role="issue"}.) - 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`{.interpreted-text role="meth"}/`!find_module`{.interpreted-text role="meth"} (superseded by `~importlib.abc.MetaPathFinder.find_spec`{.interpreted-text role="meth"}), `importlib.abc.Loader.load_module` (superseded by `~importlib.abc.Loader.exec_module`{.interpreted-text role="meth"}), `!module_repr`{.interpreted-text role="meth"} (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`{.interpreted-text role="mod"}). `ImportWarning`{.interpreted-text role="exc"} and/or `DeprecationWarning`{.interpreted-text role="exc"} 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 `{.interpreted-text role="ref"} section for more information. - Non-integer arguments to `random.randrange`{.interpreted-text role="func"} are deprecated. The `ValueError`{.interpreted-text role="exc"} is deprecated in favor of a `TypeError`{.interpreted-text role="exc"}. (Contributed by Serhiy Storchaka and Raymond Hettinger in `37319`{.interpreted-text role="issue"}.) - The various `load_module()` methods of `importlib`{.interpreted-text role="mod"} have been documented as deprecated since Python 3.6, but will now also trigger a `DeprecationWarning`{.interpreted-text role="exc"}. Use `~importlib.abc.Loader.exec_module`{.interpreted-text role="meth"} instead. (Contributed by Brett Cannon in `26131`{.interpreted-text role="issue"}.) - `!zimport.zipimporter.load_module`{.interpreted-text role="meth"} has been deprecated in preference for `~zipimport.zipimporter.exec_module`{.interpreted-text role="meth"}. (Contributed by Brett Cannon in `26131`{.interpreted-text role="issue"}.) - The use of `importlib.abc.Loader.load_module` by the import system now triggers an `ImportWarning`{.interpreted-text role="exc"} as `~importlib.abc.Loader.exec_module`{.interpreted-text role="meth"} is preferred. (Contributed by Brett Cannon in `26131`{.interpreted-text role="issue"}.) - The use of `!importlib.abc.MetaPathFinder.find_module`{.interpreted-text role="meth"} and `!importlib.abc.PathEntryFinder.find_module`{.interpreted-text role="meth"} by the import system now trigger an `ImportWarning`{.interpreted-text role="exc"} as `importlib.abc.MetaPathFinder.find_spec`{.interpreted-text role="meth"} and `importlib.abc.PathEntryFinder.find_spec`{.interpreted-text role="meth"} are preferred, respectively. You can use `importlib.util.spec_from_loader`{.interpreted-text role="func"} to help in porting. (Contributed by Brett Cannon in `42134`{.interpreted-text role="issue"}.) - The use of `!importlib.abc.PathEntryFinder.find_loader`{.interpreted-text role="meth"} by the import system now triggers an `ImportWarning`{.interpreted-text role="exc"} as `importlib.abc.PathEntryFinder.find_spec`{.interpreted-text role="meth"} is preferred. You can use `importlib.util.spec_from_loader`{.interpreted-text role="func"} to help in porting. (Contributed by Brett Cannon in `43672`{.interpreted-text role="issue"}.) - The various implementations of `!importlib.abc.MetaPathFinder.find_module`{.interpreted-text role="meth"} ( `!importlib.machinery.BuiltinImporter.find_module`{.interpreted-text role="meth"}, `!importlib.machinery.FrozenImporter.find_module`{.interpreted-text role="meth"}, `!importlib.machinery.WindowsRegistryFinder.find_module`{.interpreted-text role="meth"}, `!importlib.machinery.PathFinder.find_module`{.interpreted-text role="meth"}, `!importlib.abc.MetaPathFinder.find_module`{.interpreted-text role="meth"} ), `!importlib.abc.PathEntryFinder.find_module`{.interpreted-text role="meth"} ( `!importlib.machinery.FileFinder.find_module`{.interpreted-text role="meth"} ), and `!importlib.abc.PathEntryFinder.find_loader`{.interpreted-text role="meth"} ( `!importlib.machinery.FileFinder.find_loader`{.interpreted-text role="meth"} ) now raise `DeprecationWarning`{.interpreted-text role="exc"} and are slated for removal in Python 3.12 (previously they were documented as deprecated in Python 3.4). (Contributed by Brett Cannon in `42135`{.interpreted-text role="issue"}.) - `!importlib.abc.Finder`{.interpreted-text role="class"} is deprecated (including its sole method, `!find_module`{.interpreted-text role="meth"}). Both `importlib.abc.MetaPathFinder`{.interpreted-text role="class"} and `importlib.abc.PathEntryFinder`{.interpreted-text role="class"} no longer inherit from the class. Users should inherit from one of these two classes as appropriate instead. (Contributed by Brett Cannon in `42135`{.interpreted-text role="issue"}.) - The deprecations of `!imp`{.interpreted-text role="mod"}, `!importlib.find_loader`{.interpreted-text role="func"}, `!importlib.util.set_package_wrapper`{.interpreted-text role="func"}, `!importlib.util.set_loader_wrapper`{.interpreted-text role="func"}, `!importlib.util.module_for_loader`{.interpreted-text role="func"}, `!pkgutil.ImpImporter`{.interpreted-text role="class"}, and `!pkgutil.ImpLoader`{.interpreted-text role="class"} have all been updated to list Python 3.12 as the slated version of removal (they began raising `DeprecationWarning`{.interpreted-text role="exc"} in previous versions of Python). (Contributed by Brett Cannon in `43720`{.interpreted-text role="issue"}.) - The import system now uses the `__spec__` attribute on modules before falling back on `!module_repr`{.interpreted-text role="meth"} for a module\'s `__repr__()` method. Removal of the use of `module_repr()` is scheduled for Python 3.12. (Contributed by Brett Cannon in `42137`{.interpreted-text role="issue"}.) - `!importlib.abc.Loader.module_repr`{.interpreted-text role="meth"}, `!importlib.machinery.FrozenLoader.module_repr`{.interpreted-text role="meth"}, and `!importlib.machinery.BuiltinLoader.module_repr`{.interpreted-text role="meth"} are deprecated and slated for removal in Python 3.12. (Contributed by Brett Cannon in `42136`{.interpreted-text role="issue"}.) - `sqlite3.OptimizedUnicode` has been undocumented and obsolete since Python 3.3, when it was made an alias to `str`{.interpreted-text role="class"}. It is now deprecated, scheduled for removal in Python 3.12. (Contributed by Erlend E. Aasland in `42264`{.interpreted-text role="issue"}.) - 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](https://sqlite.org/c3ref/enable_shared_cache.html) 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 `24464`{.interpreted-text role="issue"}.) - The following `threading` methods are now deprecated: - `threading.currentThread` =\> `threading.current_thread`{.interpreted-text role="func"} - `threading.activeCount` =\> `threading.active_count`{.interpreted-text role="func"} - `threading.Condition.notifyAll` =\> `threading.Condition.notify_all`{.interpreted-text role="meth"} - `threading.Event.isSet` =\> `threading.Event.is_set`{.interpreted-text role="meth"} - `threading.Thread.setName` =\> `threading.Thread.name`{.interpreted-text role="attr"} - `threading.thread.getName` =\> `threading.Thread.name`{.interpreted-text role="attr"} - `threading.Thread.isDaemon` =\> `threading.Thread.daemon`{.interpreted-text role="attr"} - `threading.Thread.setDaemon` =\> `threading.Thread.daemon`{.interpreted-text role="attr"} (Contributed by Jelle Zijlstra in `87889`{.interpreted-text role="gh"}.) - `!pathlib.Path.link_to`{.interpreted-text role="meth"} is deprecated and slated for removal in Python 3.12. Use `pathlib.Path.hardlink_to`{.interpreted-text role="meth"} instead. (Contributed by Barney Gale in `39950`{.interpreted-text role="issue"}.) - `cgi.log()` is deprecated and slated for removal in Python 3.12. (Contributed by Inada Naoki in `41139`{.interpreted-text role="issue"}.) - The following `ssl`{.interpreted-text role="mod"} 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`{.interpreted-text role="data"}, `!OP_NO_SSLv3`{.interpreted-text role="data"}, `!OP_NO_TLSv1`{.interpreted-text role="data"}, `!OP_NO_TLSv1_1`{.interpreted-text role="data"}, `!OP_NO_TLSv1_2`{.interpreted-text role="data"}, and `!OP_NO_TLSv1_3`{.interpreted-text role="data"} are replaced by `~ssl.SSLContext.minimum_version`{.interpreted-text role="attr"} and `~ssl.SSLContext.maximum_version`{.interpreted-text role="attr"}. - `!PROTOCOL_SSLv2`{.interpreted-text role="data"}, `!PROTOCOL_SSLv3`{.interpreted-text role="data"}, `!PROTOCOL_SSLv23`{.interpreted-text role="data"}, `!PROTOCOL_TLSv1`{.interpreted-text role="data"}, `!PROTOCOL_TLSv1_1`{.interpreted-text role="data"}, `!PROTOCOL_TLSv1_2`{.interpreted-text role="data"}, and `!PROTOCOL_TLS`{.interpreted-text role="const"} are deprecated in favor of `~ssl.PROTOCOL_TLS_CLIENT`{.interpreted-text role="const"} and `~ssl.PROTOCOL_TLS_SERVER`{.interpreted-text role="const"} - `!wrap_socket`{.interpreted-text role="func"} is replaced by `ssl.SSLContext.wrap_socket`{.interpreted-text role="meth"} - `!match_hostname`{.interpreted-text role="func"} - `!RAND_pseudo_bytes`{.interpreted-text role="func"}, `!RAND_egd`{.interpreted-text role="func"} - NPN features like `ssl.SSLSocket.selected_npn_protocol`{.interpreted-text role="meth"} and `ssl.SSLContext.set_npn_protocols`{.interpreted-text role="meth"} are replaced by ALPN. - The threading debug (`!PYTHONTHREADDEBUG`{.interpreted-text role="envvar"} environment variable) is deprecated in Python 3.10 and will be removed in Python 3.12. This feature requires a `debug build of Python `{.interpreted-text role="ref"}. (Contributed by Victor Stinner in `44584`{.interpreted-text role="issue"}.) - Importing from the `typing.io` and `typing.re` submodules will now emit `DeprecationWarning`{.interpreted-text role="exc"}. These submodules will be removed in a future version of Python. Anything belonging to these submodules should be imported directly from `typing`{.interpreted-text role="mod"} instead. (Contributed by Sebastian Rittau in `38291`{.interpreted-text role="issue"}.) ## Removed {#whatsnew310-removed} - Removed special methods `__int__`, `__float__`, `__floordiv__`, `__mod__`, `__divmod__`, `__rfloordiv__`, `__rmod__` and `__rdivmod__` of the `complex`{.interpreted-text role="class"} class. They always raised a `TypeError`{.interpreted-text role="exc"}. (Contributed by Serhiy Storchaka in `41974`{.interpreted-text role="issue"}.) - The `ParserBase.error()` method from the private and undocumented `_markupbase` module has been removed. `html.parser.HTMLParser`{.interpreted-text role="class"} is the only subclass of `ParserBase` and its `error()` implementation was already removed in Python 3.5. (Contributed by Berker Peksag in `31844`{.interpreted-text role="issue"}.) - 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 `42157`{.interpreted-text role="issue"}.) - 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 `42299`{.interpreted-text role="issue"}.) - Removed the `!PyModule_GetWarningsModule`{.interpreted-text role="c:func"} function that was useless now due to the `!_warnings`{.interpreted-text role="mod"} module was converted to a builtin module in 2.6. (Contributed by Hai Shi in `42599`{.interpreted-text role="issue"}.) - Remove deprecated aliases to `collections-abstract-base-classes`{.interpreted-text role="ref"} from the `collections`{.interpreted-text role="mod"} module. (Contributed by Victor Stinner in `37324`{.interpreted-text role="issue"}.) - The `loop` parameter has been removed from most of `asyncio`{.interpreted-text role="mod"}\'s `high-level API <../library/asyncio-api-index>`{.interpreted-text role="doc"} 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 `changes-python-api`{.interpreted-text role="ref"} for examples of how to replace existing code. (Contributed by Yurii Karabas, Andrew Svetlov, Yury Selivanov and Kyle Stanley in `42392`{.interpreted-text role="issue"}.) ## 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 `43833`{.interpreted-text role="issue"}.) ### Changes in the Python API {#changes-python-api} - The *etype* parameters of the `~traceback.format_exception`{.interpreted-text role="func"}, `~traceback.format_exception_only`{.interpreted-text role="func"}, and `~traceback.print_exception`{.interpreted-text role="func"} functions in the `traceback`{.interpreted-text role="mod"} module have been renamed to *exc*. (Contributed by Zackery Spytz and Matthias Bussonnier in `26389`{.interpreted-text role="issue"}.) - `atexit`{.interpreted-text role="mod"}: At Python exit, if a callback registered with `atexit.register`{.interpreted-text role="func"} 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 `42639`{.interpreted-text role="issue"}.) - `collections.abc.Callable`{.interpreted-text role="class"} generic now flattens type parameters, similar to what `typing.Callable`{.interpreted-text role="data"} 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`{.interpreted-text role="func"} or `__args__` need to account for this change. Furthermore, `TypeError`{.interpreted-text role="exc"} may be raised for invalid forms of parameterizing `collections.abc.Callable`{.interpreted-text role="class"} which may have passed silently in Python 3.9. (Contributed by Ken Jin in `42195`{.interpreted-text role="issue"}.) - `socket.htons`{.interpreted-text role="meth"} and `socket.ntohs`{.interpreted-text role="meth"} now raise `OverflowError`{.interpreted-text role="exc"} instead of `DeprecationWarning`{.interpreted-text role="exc"} if the given parameter will not fit in a 16-bit unsigned integer. (Contributed by Erlend E. Aasland in `42393`{.interpreted-text role="issue"}.) - The `loop` parameter has been removed from most of `asyncio`{.interpreted-text role="mod"}\'s `high-level API <../library/asyncio-api-index>`{.interpreted-text role="doc"} 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`{.interpreted-text role="func"} instead. (Contributed by Yurii Karabas, Andrew Svetlov, Yury Selivanov and Kyle Stanley in `42392`{.interpreted-text role="issue"}.) - The `types.FunctionType`{.interpreted-text role="data"} 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`{.interpreted-text role="func"} and `exec`{.interpreted-text role="func"} 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 `42990`{.interpreted-text role="issue"}.) ### Changes in the C API - 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`{.interpreted-text role="c:func"}. The resulting code object can then be evaluated using, for example, `PyEval_EvalCode`{.interpreted-text role="c:func"}. Specifically: - A call to `PyParser_SimpleParseStringFlags` followed by `PyNode_Compile` can be replaced by calling `Py_CompileString`{.interpreted-text role="c:func"}. - 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`{.interpreted-text role="c:func"}. - 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`{.interpreted-text role="py:mod"} module with `PyImport_ImportModule`{.interpreted-text role="c:func"}, `PyObject_CallMethod`{.interpreted-text role="c:func"}, `PyBytes_AsString`{.interpreted-text role="c:func"} and `Py_CompileString`{.interpreted-text role="c:func"}, 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 `~frame.f_lasti`{.interpreted-text role="attr"} 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`{.interpreted-text role="c:func"} for example). Notice as well that the `!f_lasti`{.interpreted-text role="attr"} member of `FrameObject` objects is not considered stable: please use `PyFrame_GetLineNumber`{.interpreted-text role="c:func"} instead. ## CPython bytecode changes - 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 `42202`{.interpreted-text role="issue"}.) ## Build Changes - `644`{.interpreted-text role="pep"}: Python now requires OpenSSL 1.1.1 or newer. OpenSSL 1.0.2 is no longer supported. (Contributed by Christian Heimes in `43669`{.interpreted-text role="issue"}.) - The C99 functions `snprintf`{.interpreted-text role="c:func"} and `vsnprintf`{.interpreted-text role="c:func"} are now required to build Python. (Contributed by Victor Stinner in `36020`{.interpreted-text role="issue"}.) - `sqlite3`{.interpreted-text role="mod"} requires SQLite 3.7.15 or higher. (Contributed by Sergey Fedoseev and Erlend E. Aasland in `40744`{.interpreted-text role="issue"} and `40810`{.interpreted-text role="issue"}.) - The `atexit`{.interpreted-text role="mod"} module must now always be built as a built-in module. (Contributed by Victor Stinner in `42639`{.interpreted-text role="issue"}.) - Add `--disable-test-modules`{.interpreted-text role="option"} option to the `configure` script: don\'t build nor install test modules. (Contributed by Xavier de Gaye, Thomas Petazzoni and Peixing Xin in `27640`{.interpreted-text role="issue"}.) - Add `--with-wheel-pkg-dir=PATH option <--with-wheel-pkg-dir>`{.interpreted-text role="option"} to the `./configure` script. If specified, the `ensurepip`{.interpreted-text role="mod"} 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 `42856`{.interpreted-text role="issue"}.) - Add a new `configure --without-static-libpython option <--without-static-libpython>`{.interpreted-text role="option"} to not build the `libpythonMAJOR.MINOR.a` static library and not install the `python.o` object file. (Contributed by Victor Stinner in `43103`{.interpreted-text role="issue"}.) - 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 `42603`{.interpreted-text role="issue"}.) - Add `--with-openssl-rpath`{.interpreted-text role="option"} 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 `43466`{.interpreted-text role="issue"}.) ## C API Changes ### PEP 652: Maintaining the Stable ABI The Stable ABI (Application Binary Interface) for extension modules or embedding Python is now explicitly defined. `stable`{.interpreted-text role="ref"} describes C API and ABI stability guarantees along with best practices for using the Stable ABI. (Contributed by Petr Viktorin in `652`{.interpreted-text role="pep"} and `43795`{.interpreted-text role="issue"}.) ### New Features - The result of `PyNumber_Index`{.interpreted-text role="c:func"} now always has exact type `int`{.interpreted-text role="class"}. Previously, the result could have been an instance of a subclass of `int`. (Contributed by Serhiy Storchaka in `40792`{.interpreted-text role="issue"}.) - Add a new `~PyConfig.orig_argv`{.interpreted-text role="c:member"} member to the `PyConfig`{.interpreted-text role="c:type"} structure: the list of the original command line arguments passed to the Python executable. (Contributed by Victor Stinner in `23427`{.interpreted-text role="issue"}.) - The `PyDateTime_DATE_GET_TZINFO`{.interpreted-text role="c:func"} and `PyDateTime_TIME_GET_TZINFO`{.interpreted-text role="c:func"} macros have been added for accessing the `tzinfo` attributes of `datetime.datetime`{.interpreted-text role="class"} and `datetime.time`{.interpreted-text role="class"} objects. (Contributed by Zackery Spytz in `30155`{.interpreted-text role="issue"}.) - Add a `PyCodec_Unregister`{.interpreted-text role="c:func"} function to unregister a codec search function. (Contributed by Hai Shi in `41842`{.interpreted-text role="issue"}.) - The `PyIter_Send`{.interpreted-text role="c:func"} function was added to allow sending value into iterator without raising `StopIteration` exception. (Contributed by Vladimir Matveev in `41756`{.interpreted-text role="issue"}.) - Add `PyUnicode_AsUTF8AndSize`{.interpreted-text role="c:func"} to the limited C API. (Contributed by Alex Gaynor in `41784`{.interpreted-text role="issue"}.) - Add `PyModule_AddObjectRef`{.interpreted-text role="c:func"} function: similar to `PyModule_AddObject`{.interpreted-text role="c:func"} but don\'t steal a reference to the value on success. (Contributed by Victor Stinner in `1635741`{.interpreted-text role="issue"}.) - Add `Py_NewRef`{.interpreted-text role="c:func"} and `Py_XNewRef`{.interpreted-text role="c:func"} functions to increment the reference count of an object and return the object. (Contributed by Victor Stinner in `42262`{.interpreted-text role="issue"}.) - The `PyType_FromSpecWithBases`{.interpreted-text role="c:func"} and `PyType_FromModuleAndSpec`{.interpreted-text role="c:func"} functions now accept a single class as the *bases* argument. (Contributed by Serhiy Storchaka in `42423`{.interpreted-text role="issue"}.) - The `PyType_FromModuleAndSpec`{.interpreted-text role="c:func"} function now accepts NULL `tp_doc` slot. (Contributed by Hai Shi in `41832`{.interpreted-text role="issue"}.) - The `PyType_GetSlot`{.interpreted-text role="c:func"} function can accept `static types `{.interpreted-text role="ref"}. (Contributed by Hai Shi and Petr Viktorin in `41073`{.interpreted-text role="issue"}.) - Add a new `PySet_CheckExact`{.interpreted-text role="c:func"} function to the C-API to check if an object is an instance of `set`{.interpreted-text role="class"} but not an instance of a subtype. (Contributed by Pablo Galindo in `43277`{.interpreted-text role="issue"}.) - Add `PyErr_SetInterruptEx`{.interpreted-text role="c:func"} which allows passing a signal number to simulate. (Contributed by Antoine Pitrou in `43356`{.interpreted-text role="issue"}.) - The limited C API is now supported if `Python is built in debug mode `{.interpreted-text role="ref"} (if the `Py_DEBUG` macro is defined). In the limited C API, the `Py_INCREF`{.interpreted-text role="c:func"} and `Py_DECREF`{.interpreted-text role="c:func"} functions are now implemented as opaque function calls, rather than accessing directly the `PyObject.ob_refcnt`{.interpreted-text role="c:member"} 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`{.interpreted-text role="c:type"} structure is the same in release and debug mode since Python 3.8 (see `36465`{.interpreted-text role="issue"}). The limited C API is still not supported in the `--with-trace-refs`{.interpreted-text role="option"} special build (`Py_TRACE_REFS` macro). (Contributed by Victor Stinner in `43688`{.interpreted-text role="issue"}.) - Add the `Py_Is(x, y) `{.interpreted-text role="c:func"} function to test if the *x* object is the *y* object, the same as `x is y` in Python. Add also the `Py_IsNone`{.interpreted-text role="c:func"}, `Py_IsTrue`{.interpreted-text role="c:func"}, `Py_IsFalse`{.interpreted-text role="c:func"} functions to test if an object is, respectively, the `None` singleton, the `True` singleton or the `False` singleton. (Contributed by Victor Stinner in `43753`{.interpreted-text role="issue"}.) - Add new functions to control the garbage collector from C code: `PyGC_Enable()`{.interpreted-text role="c:func"}, `PyGC_Disable()`{.interpreted-text role="c:func"}, `PyGC_IsEnabled()`{.interpreted-text role="c:func"}. These functions allow to activate, deactivate and query the state of the garbage collector from C code without having to import the `gc`{.interpreted-text role="mod"} module. - Add a new `Py_TPFLAGS_DISALLOW_INSTANTIATION`{.interpreted-text role="c:macro"} type flag to disallow creating type instances. (Contributed by Victor Stinner in `43916`{.interpreted-text role="issue"}.) - Add a new `Py_TPFLAGS_IMMUTABLETYPE`{.interpreted-text role="c:macro"} type flag for creating immutable type objects: type attributes cannot be set nor deleted. (Contributed by Victor Stinner and Erlend E. Aasland in `43908`{.interpreted-text role="issue"}.) ### Porting to Python 3.10 - The `PY_SSIZE_T_CLEAN` macro must now be defined to use `PyArg_ParseTuple`{.interpreted-text role="c:func"} and `Py_BuildValue`{.interpreted-text role="c:func"} formats which use `#`: `es#`, `et#`, `s#`, `u#`, `y#`, `z#`, `U#` and `Z#`. See `arg-parsing`{.interpreted-text role="ref"} and `353`{.interpreted-text role="pep"}. (Contributed by Victor Stinner in `40943`{.interpreted-text role="issue"}.) - Since `Py_REFCNT()`{.interpreted-text role="c:func"} 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()`{.interpreted-text role="c:func"} (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 `39573`{.interpreted-text role="issue"}.) - Calling `PyDict_GetItem`{.interpreted-text role="c:func"} without `GIL`{.interpreted-text role="term"} held had been allowed for historical reason. It is no longer allowed. (Contributed by Victor Stinner in `40839`{.interpreted-text role="issue"}.) - `PyUnicode_FromUnicode(NULL, size)` and `PyUnicode_FromStringAndSize(NULL, size)` raise `DeprecationWarning` now. Use `PyUnicode_New`{.interpreted-text role="c:func"} to allocate Unicode object without initial data. (Contributed by Inada Naoki in `36346`{.interpreted-text role="issue"}.) - 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 `42157`{.interpreted-text role="issue"}.) - `!Py_GetPath`{.interpreted-text role="c:func"}, `!Py_GetPrefix`{.interpreted-text role="c:func"}, `!Py_GetExecPrefix`{.interpreted-text role="c:func"}, `!Py_GetProgramFullPath`{.interpreted-text role="c:func"}, `!Py_GetPythonHome`{.interpreted-text role="c:func"} and `!Py_GetProgramName`{.interpreted-text role="c:func"} functions now return `NULL` if called before `Py_Initialize`{.interpreted-text role="c:func"} (before Python is initialized). Use the new `init-config`{.interpreted-text role="ref"} API to get the `init-path-config`{.interpreted-text role="ref"}. (Contributed by Victor Stinner in `42260`{.interpreted-text role="issue"}.) - `PyList_SET_ITEM`{.interpreted-text role="c:func"}, `PyTuple_SET_ITEM`{.interpreted-text role="c:func"} and `PyCell_SET`{.interpreted-text role="c:func"} 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 `30459`{.interpreted-text role="issue"}.) - 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 `api-includes`{.interpreted-text role="ref"}. If they have been included directly, consider including `Python.h` instead. (Contributed by Nicholas Sim in `35134`{.interpreted-text role="issue"}.) - Use the `Py_TPFLAGS_IMMUTABLETYPE`{.interpreted-text role="c:macro"} type flag to create immutable type objects. Do not rely on `Py_TPFLAGS_HEAPTYPE`{.interpreted-text role="c:macro"} to decide if a type object is mutable or not; check if `Py_TPFLAGS_IMMUTABLETYPE`{.interpreted-text role="c:macro"} is set instead. (Contributed by Victor Stinner and Erlend E. Aasland in `43908`{.interpreted-text role="issue"}.) - 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 `26241`{.interpreted-text role="issue"}.) ### Deprecated - The `PyUnicode_InternImmortal()` function is now deprecated and will be removed in Python 3.12: use `PyUnicode_InternInPlace`{.interpreted-text role="c:func"} instead. (Contributed by Victor Stinner in `41692`{.interpreted-text role="issue"}.) ### Removed - Removed `Py_UNICODE_str*` functions manipulating `Py_UNICODE*` strings. (Contributed by Inada Naoki in `41123`{.interpreted-text role="issue"}.) - `Py_UNICODE_strlen`: use `PyUnicode_GetLength`{.interpreted-text role="c:func"} or `PyUnicode_GET_LENGTH`{.interpreted-text role="c:macro"} - `Py_UNICODE_strcat`: use `PyUnicode_CopyCharacters`{.interpreted-text role="c:func"} or `PyUnicode_FromFormat`{.interpreted-text role="c:func"} - `Py_UNICODE_strcpy`, `Py_UNICODE_strncpy`: use `PyUnicode_CopyCharacters`{.interpreted-text role="c:func"} or `PyUnicode_Substring`{.interpreted-text role="c:func"} - `Py_UNICODE_strcmp`: use `PyUnicode_Compare`{.interpreted-text role="c:func"} - `Py_UNICODE_strncmp`: use `PyUnicode_Tailmatch`{.interpreted-text role="c:func"} - `Py_UNICODE_strchr`, `Py_UNICODE_strrchr`: use `PyUnicode_FindChar`{.interpreted-text role="c:func"} - Removed `PyUnicode_GetMax()`. Please migrate to new (`393`{.interpreted-text role="pep"}) APIs. (Contributed by Inada Naoki in `41103`{.interpreted-text role="issue"}.) - Removed `PyLong_FromUnicode()`. Please migrate to `PyLong_FromUnicodeObject`{.interpreted-text role="c:func"}. (Contributed by Inada Naoki in `41103`{.interpreted-text role="issue"}.) - Removed `PyUnicode_AsUnicodeCopy()`. Please use `PyUnicode_AsUCS4Copy`{.interpreted-text role="c:func"} or `PyUnicode_AsWideCharString`{.interpreted-text role="c:func"} (Contributed by Inada Naoki in `41103`{.interpreted-text role="issue"}.) - Removed `_Py_CheckRecursionLimit` variable: it has been replaced by `ceval.recursion_limit` of the `PyInterpreterState`{.interpreted-text role="c:type"} structure. (Contributed by Victor Stinner in `41834`{.interpreted-text role="issue"}.) - Removed undocumented macros `Py_ALLOW_RECURSION` and `Py_END_ALLOW_RECURSION` and the `recursion_critical` field of the `PyInterpreterState`{.interpreted-text role="c:type"} structure. (Contributed by Serhiy Storchaka in `41936`{.interpreted-text role="issue"}.) - Removed the undocumented `PyOS_InitInterrupts()` function. Initializing Python already implicitly installs signal handlers: see `PyConfig.install_signal_handlers`{.interpreted-text role="c:member"}. (Contributed by Victor Stinner in `41713`{.interpreted-text role="issue"}.) - 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 (`384`{.interpreted-text role="pep"}). (Contributed by Victor Stinner in `43244`{.interpreted-text role="issue"}.) - 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`{.interpreted-text role="mod"} module instead. (Contributed by Victor Stinner in `43244`{.interpreted-text role="issue"}.) - Remove `PyOS_ReadlineFunctionPointer`{.interpreted-text role="c:func"} 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 `43868`{.interpreted-text role="issue"}.) - 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 `` header. Use the Python `ast`{.interpreted-text role="mod"} module instead. (Contributed by Victor Stinner in `43244`{.interpreted-text role="issue"}.) - 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 `43244`{.interpreted-text role="issue"}.) - 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 `43244`{.interpreted-text role="issue"}.) - The `PyThreadState.use_tracing` member has been removed to optimize Python. (Contributed by Mark Shannon in `43760`{.interpreted-text role="issue"}.) ## Notable security feature in 3.10.7 Converting between `int`{.interpreted-text role="class"} and `str`{.interpreted-text role="class"} in bases other than 2 (binary), 4, 8 (octal), 16 (hexadecimal), or 32 such as base 10 (decimal) now raises a `ValueError`{.interpreted-text role="exc"} 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 `2020-10735`{.interpreted-text role="cve"}. This limit can be configured or disabled by environment variable, command line flag, or `sys`{.interpreted-text role="mod"} APIs. See the `integer string conversion length limitation `{.interpreted-text role="ref"} documentation. The default limit is 4300 digits in string form. ## Notable security feature in 3.10.8 The deprecated `!mailcap`{.interpreted-text role="mod"} 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 `98966`{.interpreted-text role="gh"}.) ## Notable changes in 3.10.12 ### tarfile - The extraction methods in `tarfile`{.interpreted-text role="mod"}, and `shutil.unpack_archive`{.interpreted-text role="func"}, 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 `tarfile-extraction-filter`{.interpreted-text role="ref"} for details. In Python 3.12, use without the *filter* argument will show a `DeprecationWarning`{.interpreted-text role="exc"}. In Python 3.14, the default will switch to `'data'`. (Contributed by Petr Viktorin in `706`{.interpreted-text role="pep"}.)