Python >=3.10 required.

.github/workflows/build.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ['3.9', '3.10', '3.11', '3.12', '3.13', '3.14.0-alpha - 3.14']
+        python-version: ['3.10', '3.11', '3.12', '3.13', '3.14.0-alpha - 3.14']
     steps:
     - uses: actions/checkout@v4
     - uses: actions/setup-python@v5

CHANGELOG.md

@@ -4,6 +4,8 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ## Unreleased
+### Changed
+* Python >=3.10 required
 
 ## [2.0](https://pypi.org/project/multimethod/2.0/) - 2024-12-26
 ### Removed

multimethod/__init__.py

@@ -7,7 +7,7 @@
 import types
 import typing
 from collections.abc import Callable, Iterable, Iterator, Mapping
-from typing import Any, Literal, Optional, TypeVar, Union, get_type_hints, overload
+from typing import Any, Literal, TypeVar, Union, get_type_hints, overload
 
 
 class DispatchError(TypeError):
@@ -57,15 +57,14 @@ def __new__(cls, tp, *args):
         if isinstance(tp, typing._AnnotatedAlias):
             return cls(tp.__origin__, *args)
         origin = get_origin(tp) or tp
-        if hasattr(types, 'UnionType') and isinstance(tp, types.UnionType):
-            origin = Union  # `|` syntax added in 3.10
         args = tuple(map(cls, get_args(tp) or args))
         if set(args) <= {object} and not (origin is tuple and args):
             return origin
         bases = (origin,) if type(origin) in (type, abc.ABCMeta) else ()
         if origin is Literal:
             bases = (cls(Union[tuple(map(type, args))]),)
-        if origin is Union:
+        if origin is Union or isinstance(tp, types.UnionType):
+            origin = types.UnionType
             bases = common_bases(*args)[:1]
             if bases[0] in args:
                 return bases[0]
@@ -90,11 +89,11 @@ def __subclasscheck__(self, subclass):
         args = get_args(subclass)
         if origin is Literal:
             return all(isinstance(arg, self) for arg in args)
-        if origin is Union:
+        if origin in (Union, types.UnionType):
             return all(issubclass(cls, self) for cls in args)
         if self.__origin__ is Literal:
             return False
-        if self.__origin__ is Union:
+        if self.__origin__ is types.UnionType:
             return issubclass(subclass, self.__args__)
         if self.__origin__ is Callable:
             return (
@@ -111,7 +110,7 @@ def __subclasscheck__(self, subclass):
     def __instancecheck__(self, instance):
         if self.__origin__ is Literal:
             return any(type(arg) is type(instance) and arg == instance for arg in self.__args__)
-        if self.__origin__ is Union:
+        if self.__origin__ is types.UnionType:
             return isinstance(instance, self.__args__)
         if hasattr(instance, '__orig_class__'):  # user-defined generic type
             return issubclass(instance.__orig_class__, self)
@@ -139,7 +138,7 @@ def origins(self) -> Iterable[type]:
         origin = get_origin(self)
         if origin is Literal:
             yield from set(map(type, self.__args__))
-        elif origin is Union:
+        elif origin is types.UnionType:
             for arg in self.__args__:
                 yield from subtype.origins(arg)
         elif origin is not None:
@@ -192,10 +191,10 @@ class signature(tuple):
     parents: set
     sig: inspect.Signature
 
-    def __new__(cls, types: Iterable, required: Optional[int] = None):
+    def __new__(cls, types: Iterable, required: int | None = None):
         return tuple.__new__(cls, map(subtype, types))
 
-    def __init__(self, types: Iterable, required: Optional[int] = None):
+    def __init__(self, types: Iterable, required: int | None = None):
         self.required = len(self) if required is None else required
 
     @classmethod

pyproject.toml

@@ -3,7 +3,7 @@ name = "multimethod"
 version = "2.0"
 description = "Multiple argument dispatching."
 readme = "README.md"
-requires-python = ">=3.9"
+requires-python = ">=3.10"
 license = {file = "LICENSE.txt"}
 authors = [{name = "Aric Coady", email = "[email protected]"}]
 keywords = ["multiple", "dispatch", "multidispatch", "generic", "functions", "methods", "overload"]
@@ -13,7 +13,6 @@ classifiers = [
     "License :: OSI Approved :: Apache Software License",
     "Operating System :: OS Independent",
     "Programming Language :: Python :: 3",
-    "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",