collections Container datatypes Python 3 14.5rc1 documentation

The first argument to Annotated must be a valid type. A tool or library encountering an Annotated typecan scan through the metadata elements to determine if they are of interest(e.g., using isinstance()). Add metadata x to a given type T by using the annotationAnnotatedT, x. Special typing form to add context-specific metadata to an annotation.

The library changes contain removal of deprecated APIs and modules,as well as the usual improvements in user-friendliness and correctness.Several legacy standard library modules have now been removed following their deprecation in Python 3.11 (PEP 594). Error messages continue to improve, with tracebacks now highlighted in colorby default. Python 3.13 is a stable release of the Python programminglanguage, with a mix of changes to the language, the implementationand the standard library.The biggest changes include a new interactive interpreter,experimental support for running in a free-threaded mode (PEP 703),and a Just-In-Time compiler (PEP 744).

Removed C APIs¶

Initially PEP 484 defined the Python static type system as usingnominal subtyping. Contrast the behavior of Any with the behavior of object.Similar to Any, every type is a subtype of object. A generic type can have any number of type variables. Generic classes implicitly inherit from Generic. This also makes T valid asa type within the class body.

They are intendedfor runtime introspection and have no special meaning to static type checkers. Only parameter specification variables defined in global scope canbe pickled. Bothattributes require the annotated parameter to be in scope. Since ParamSpec captures both positional and keyword parameters,P.args and P.kwargs can be used to split a ParamSpec into itscomponents.

The default encoding of TextIOWrapper and open() isplatform and locale dependent. While structural pattern matching can be used in itssimplest form comparing a variable to a literal in a case statement, itstrue value for Python lies in its handling of the subject’s type and shape. Often the switch statementis used for comparison of an object/expression with case statements containingliterals. Notice this won’t work if PyErr_Display() is not called to display the error,which can happen if some other custom error display function is used.

The Python typing system is standardised via PEPs, so this referenceshould broadly apply to most Python type checkers. New features are frequently added to the typing module.The typing_extensions packageprovides backports of these new features to older versions of Python. The typing module provides a vocabulary ofmore advanced type hints. This module provides runtime support for type hints. See the integer string conversionlength limitation documentation.

• The index() method of array.array now hasoptional start and stop parameters.(Contributed by Anders Lorentsen and Zackery Spytz in bpo-31956.)
• ABC for classes that provide an __aiter__ method.
• Literal objectswill now raise a TypeError exception during equality comparisonsif one of their parameters are not hashable.
• It is not possible to assign to the individualitems of a tuple, however it is possible to create tuples which contain mutableobjects, such as lists.

Pending removal in Python 3.13¶

Provides a runtime callback that returns thedefault value for the field. Decorator to mark an object as providingdataclass-like behavior. When a static type checker encounters a call to this function,it emits a diagnostic with the inferred type of the argument.

The non-@overload-decorateddefinition, meanwhile, will be used atruntime but should be ignored by a type checker. @overload-decorated definitions are for the benefit of thetype checker only, since they will be overwritten by thenon-@overload-decorated definition. This alternativename is used in the synthesized __init__ method. Indicates whether the field should be included in thesynthesized __init__ method. Importing the name fromtyping, however, allows your code to run without runtime errors andcommunicates intent more clearly.

Decorating a class with @finalindicates that it cannot be subclassed. Get_overloads() can be used for introspecting an overloaded function atruntime. See PEP 484 for more details and comparison with other typing semantics. At runtime, callingan @overload-decorated function directly will raiseNotImplementedError.

Special type that includes only literal strings. AnyStr will be removed from typingin Python 3.18. In Python 3.16, AnyStr will be removed from typing.__all__, anddeprecation warnings will be emitted at runtime when it is accessed orimported from typing. Note that, despite its name, AnyStr has nothing to do with theAny type, nor does it mean “any string”. AnyStr is meant to be used for functions that may accept str orbytes arguments but cannot allow the khelovip bangladesh two to mix. Special type indicating an unconstrained type.