Drop support for Python 3.9 (#916)

Author: mauvilsa

.github/workflows/manual.yaml

@@ -20,7 +20,6 @@ jobs:
       - uses: actions/setup-python@a309ff8b426b58ec0e2a45f0f869d46889d02405  # v6.2.0
         with:
           python-version: |
-            3.9
             3.10
             3.11
             3.12

.github/workflows/tests.yaml

@@ -19,7 +19,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python: ["3.9", "3.10", "3.11", "3.12", "3.13", "3.14"]
+        python: ["3.10", "3.11", "3.12", "3.13", "3.14"]
     steps:
       - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd  # v6.0.2
       - uses: actions/setup-python@a309ff8b426b58ec0e2a45f0f869d46889d02405  # v6.2.0
@@ -267,7 +267,7 @@ jobs:
             -Dsonar.exclusions=sphinx/**
             -Dsonar.tests=jsonargparse_tests
             -Dsonar.python.coverage.reportPaths=coverage_*.xml
-            -Dsonar.python.version=3.9,3.10,3.11,3.12,3.13,3.14
+            -Dsonar.python.version=3.10,3.11,3.12,3.13,3.14
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}  # Needed to get PR information, if any
           SONAR_TOKEN: ${{ secrets.SONAR_TOKEN }}

CHANGELOG.rst

@@ -12,6 +12,15 @@ The semantic versioning only considers the public API as described in
 paths are considered internals and can change in minor and patch releases.
 
 
+v4.50.0 (unreleased)
+--------------------
+
+Changed
+^^^^^^^
+- Drop support for Python 3.9. The minimum supported Python version is now
+  3.10 (`#916 <https://github.com/omni-us/jsonargparse/pull/916>`__).
+
+
 v4.49.0 (2026-05-15)
 --------------------
 

DOCUMENTATION.rst

@@ -443,9 +443,11 @@ Some notes about this support are:
   limit in nesting depth.
 
 - Postponed evaluation of types PEP `563 <https://peps.python.org/pep-0563/>`__
-  (i.e. ``from __future__ import annotations``) is supported. Also supported on
-  ``python==3.9`` is PEP `604 <https://peps.python.org/pep-0604/>`__ (i.e.
-  ``<type> | <type>`` instead of ``Union[<type>, <type>]``).
+  (i.e. ``from __future__ import annotations``) is supported. Also supported are
+  PEP `585 <https://peps.python.org/pep-0585/>`__ (i.e. ``list[<type>],
+  dict[<type>], ...`` instead of ``List[<type>], Dict[<type>], ...``) and `604
+  <https://peps.python.org/pep-0604/>`__ (i.e. ``<type> | <type>`` instead of
+  ``Union[<type>, <type>]``).
 
 - Types that use components imported inside ``TYPE_CHECKING`` blocks are
   supported.
@@ -1875,9 +1877,7 @@ jsonargparse with the ``signatures`` extra as explained in section
 
 Many of the types defined in stub files use the latest syntax for type hints,
 that is, bitwise or operator ``|`` for unions, see PEP `604
-<https://peps.python.org/pep-0604>`__. On ``python>=3.10`` these are fully
-supported. On ``python<=3.9`` backporting these types is attempted and in some
-cases it can fail. On failure the type annotation is set to ``Any``.
+<https://peps.python.org/pep-0604>`__. This syntax is fully supported.
 
 Most of the types in the Python standard library have their types in stubs. An
 example from the standard library would be:

jsonargparse/_actions.py

@@ -6,7 +6,7 @@
 from argparse import Action as ArgparseAction
 from contextlib import contextmanager
 from contextvars import ContextVar
-from typing import Any, Optional
+from typing import Any
 
 from ._common import Action, NonParsingAction, is_subclass, is_subclasses_disabled, parser_context
 from ._loaders_dumpers import get_loader_exceptions, load_value
@@ -116,7 +116,7 @@ def apply_config(parser, cfg, dest, value) -> None:
         with parser_context(single_subcommand=False), previous_config_context(cfg), skip_apply_links():
             kwargs = {"env": False, "defaults": False, "_skip_validation": True, "_fail_no_subcommand": False}
             try:
-                cfg_path: Optional[Path] = Path(value, mode=_get_config_read_mode())
+                cfg_path: Path | None = Path(value, mode=_get_config_read_mode())
             except TypeError as ex_path:
                 try:
                     if isinstance(load_value(value), str):
@@ -224,7 +224,7 @@ def is_print_config_requested(parser):
 
 
 class _ActionConfigLoad(Action):
-    def __init__(self, basetype: Optional[type] = None, **kwargs):
+    def __init__(self, basetype: type | None = None, **kwargs):
         if len(kwargs) == 0:
             self._basetype = basetype
         else:
@@ -267,7 +267,7 @@ class _ActionHelpClassPath(NonParsingAction):
     sub_add_kwargs: dict[str, Any] = {}
 
     @classmethod
-    def get_help_types(cls, typehint) -> Optional[tuple]:
+    def get_help_types(cls, typehint) -> tuple | None:
         from ._typehints import get_subclass_or_closed_types
 
         return get_subclass_or_closed_types(typehint=typehint, also_lists=True, callable_return=True)

jsonargparse/_cli.py

@@ -1,7 +1,8 @@
 """Simple creation of command line interfaces."""
 
 import inspect
-from typing import Any, Callable, Optional, Union
+from collections.abc import Callable
+from typing import Any, Optional, Union
 
 from ._actions import ActionConfigFile, _ActionPrintConfig, remove_actions
 from ._core import ArgumentParser
@@ -25,9 +26,9 @@ def CLI(*args, **kwargs):
 
 def auto_cli(
     components: ComponentsType = None,
-    args: Optional[list[str]] = None,
+    args: list[str] | None = None,
     config_help: str = default_config_option_help,
-    set_defaults: Optional[dict[str, Any]] = None,
+    set_defaults: dict[str, Any] | None = None,
     as_positional: bool = True,
     return_instance: bool = False,
     fail_untyped: bool = True,

jsonargparse/_common.py

@@ -3,15 +3,14 @@
 import inspect
 import logging
 import os
+from collections.abc import Callable
 from contextlib import contextmanager
 from contextvars import ContextVar
 from typing import (  # type: ignore[attr-defined]
-    Callable,
     Generic,
     Optional,
     Protocol,
     TypeVar,
-    Union,
     _GenericAlias,
 )
 
@@ -52,17 +51,17 @@ def __call__(self, class_type: type[ClassType], *args, **kwargs) -> ClassType:
 InstantiatorsDictType = dict[tuple[type, bool], InstantiatorCallable]
 
 
-parent_parser: ContextVar[Optional[ArgumentParser]] = ContextVar("parent_parser", default=None)
+parent_parser: ContextVar[ArgumentParser | None] = ContextVar("parent_parser", default=None)
 parser_capture: ContextVar[bool] = ContextVar("parser_capture", default=False)
-defaults_cache: ContextVar[Optional[Namespace]] = ContextVar("defaults_cache", default=None)
-lenient_check: ContextVar[Union[bool, str]] = ContextVar("lenient_check", default=False)
+defaults_cache: ContextVar[Namespace | None] = ContextVar("defaults_cache", default=None)
+lenient_check: ContextVar[bool | str] = ContextVar("lenient_check", default=False)
 parsing_defaults: ContextVar[bool] = ContextVar("parsing_defaults", default=False)
 single_subcommand: ContextVar[bool] = ContextVar("single_subcommand", default=True)
 validating_defaults: ContextVar[bool] = ContextVar("validating_defaults", default=False)
-load_value_mode: ContextVar[Optional[str]] = ContextVar("load_value_mode", default=None)
-class_instantiators: ContextVar[Optional[InstantiatorsDictType]] = ContextVar("class_instantiators", default=None)
+load_value_mode: ContextVar[str | None] = ContextVar("load_value_mode", default=None)
+class_instantiators: ContextVar[InstantiatorsDictType | None] = ContextVar("class_instantiators", default=None)
 nested_links: ContextVar[list[dict]] = ContextVar("nested_links", default=[])
-applied_instantiation_links: ContextVar[Optional[set]] = ContextVar("applied_instantiation_links", default=None)
+applied_instantiation_links: ContextVar[set | None] = ContextVar("applied_instantiation_links", default=None)
 path_dump_preserve_relative: ContextVar[bool] = ContextVar("path_dump_preserve_relative", default=False)
 
 
@@ -115,17 +114,17 @@ def get_env_var_bool(name: str) -> bool:
 
 def set_parsing_settings(
     *,
-    validate_defaults: Optional[bool] = None,
-    config_read_mode_urls_enabled: Optional[bool] = None,
-    config_read_mode_fsspec_enabled: Optional[bool] = None,
+    validate_defaults: bool | None = None,
+    config_read_mode_urls_enabled: bool | None = None,
+    config_read_mode_fsspec_enabled: bool | None = None,
     docstring_parse_style: Optional["docstring_parser.DocstringStyle"] = None,
-    docstring_parse_attribute_docstrings: Optional[bool] = None,
-    parse_optionals_as_positionals: Optional[bool] = None,
-    add_print_completion_argument: Optional[bool] = None,
-    stubs_resolver_allow_py_files: Optional[bool] = None,
-    omegaconf_absolute_to_relative_paths: Optional[bool] = None,
-    subclasses_disabled: Optional[list[Union[type, Callable[[type], bool]]]] = None,
-    subclasses_enabled: Optional[list[Union[type, str]]] = None,
+    docstring_parse_attribute_docstrings: bool | None = None,
+    parse_optionals_as_positionals: bool | None = None,
+    add_print_completion_argument: bool | None = None,
+    stubs_resolver_allow_py_files: bool | None = None,
+    omegaconf_absolute_to_relative_paths: bool | None = None,
+    subclasses_disabled: list[type | Callable[[type], bool]] | None = None,
+    subclasses_enabled: list[type | str] | None = None,
 ) -> None:
     """
     Modify global parser settings that affect parser creation and parsing behavior.
@@ -329,7 +328,7 @@ def is_pure_dataclass(cls) -> bool:
 
 subclasses_enabled_types: set[type] = set()
 subclasses_disabled_types: set[type] = set()
-subclasses_disabled_selectors: dict[str, Callable[[type], Union[bool, int]]] = {
+subclasses_disabled_selectors: dict[str, Callable[[type], bool | int]] = {
     "is_pure_dataclass": is_pure_dataclass,
     "is_pydantic_model": is_pydantic_model,
     "is_attrs_class": is_attrs_class,
@@ -351,8 +350,8 @@ def is_subclasses_disabled(cls) -> bool:
 
 
 def subclass_type_behavior(
-    subclasses_disabled: Optional[list[Union[type, Callable[[type], bool]]]] = None,
-    subclasses_enabled: Optional[list[Union[type, str]]] = None,
+    subclasses_disabled: list[type | Callable[[type], bool]] | None = None,
+    subclasses_enabled: list[type | str] | None = None,
 ) -> None:
     """Configures whether class types accept or not subclasses."""
     for enable_item in subclasses_enabled or []:
@@ -404,7 +403,7 @@ def setup_default_logger(data, level, caller):
     return logger
 
 
-def parse_logger(logger: Union[bool, str, dict, logging.Logger], caller):
+def parse_logger(logger: bool | str | dict | logging.Logger, caller):
     if not isinstance(logger, (bool, str, dict, logging.Logger)):
         raise ValueError(f"Expected logger to be an instance of (bool, str, dict, logging.Logger), but got {logger}.")
     if isinstance(logger, dict) and len(set(logger) - {"name", "level"}) > 0:
@@ -425,7 +424,7 @@ def parse_logger(logger: Union[bool, str, dict, logging.Logger], caller):
 class LoggerProperty:
     """Class designed to be inherited by other classes to add a logger property."""
 
-    def __init__(self, *args, logger: Union[bool, str, dict, logging.Logger] = False, **kwargs):
+    def __init__(self, *args, logger: bool | str | dict | logging.Logger = False, **kwargs):
         self.logger = logger
         super().__init__(*args, **kwargs)
 
@@ -444,7 +443,7 @@ def logger(self) -> logging.Logger:
         return self._logger
 
     @logger.setter
-    def logger(self, logger: Union[bool, str, dict, logging.Logger]):
+    def logger(self, logger: bool | str | dict | logging.Logger):
         if logger is None:
             from ._deprecated import deprecation_warning, logger_property_none_message
 

jsonargparse/_completions.py

@@ -10,7 +10,7 @@
 from enum import Enum
 from importlib.util import find_spec
 from subprocess import PIPE, Popen
-from typing import Literal, Optional, Union
+from typing import Literal, Union
 
 from ._actions import ActionConfigFile, ActionFail, _ActionConfigLoad, _ActionHelpClassPath, remove_actions
 from ._common import NonParsingAction, get_optionals_as_positionals_actions, get_parsing_setting
@@ -141,7 +141,7 @@ def get_completion_script(parser, completion_type: str, **kwargs) -> str:
     return get_shtab_script(parser, completion_type[len("shtab-") :], **kwargs)
 
 
-def get_shtab_script(parser, shell: str, preambles: Optional[list[str]] = None) -> str:
+def get_shtab_script(parser, shell: str, preambles: list[str] | None = None) -> str:
     import shtab
 
     if shell not in shtab.SUPPORTED_SHELLS: