Drop support for Python 3.9 and require 3.10 minimum (#1473)

* Drop support for Python 3.9 and require 3.10 minimum

The primary change is that type hints now support the `|` opertor and both `Optional` and `Union` are needed much less frequently from the typing module.

Also:
- Upgrade versions of ruff and prettier used by pre-commit

* Restored some comments.

---------

Co-authored-by: Kevin Van Brunt <kmvanbrunt@gmail.com>

Author: tleonhardt

.github/CONTRIBUTING.md

@@ -62,7 +62,7 @@ See the `dependencies` list under the `[project]` heading in [pyproject.toml](..
 
 | Prerequisite                                        | Minimum Version | Purpose                                |
 | --------------------------------------------------- | --------------- | -------------------------------------- |
-| [python](https://www.python.org/downloads/)         | `3.9`           | Python programming language            |
+| [python](https://www.python.org/downloads/)         | `3.10`          | Python programming language            |
 | [pyperclip](https://github.com/asweigart/pyperclip) | `1.8`           | Cross-platform clipboard functions     |
 | [wcwidth](https://pypi.python.org/pypi/wcwidth)     | `0.2.10`        | Measure the displayed width of unicode |
 
@@ -520,13 +520,11 @@ on how to do it.
 
 4. The title (also called the subject) of your PR should be descriptive of your changes and
    succinctly indicate what is being fixed
-
     - **Do not add the issue number in the PR title or commit message**
 
     - Examples: `Add test cases for Unicode support`; `Correct typo in overview documentation`
 
 5. In the body of your PR include a more detailed summary of the changes you made and why
-
     - If the PR is meant to fix an existing bug/issue, then, at the end of your PR's description,
       append the keyword `closes` and #xxxx (where xxxx is the issue number). Example:
       `closes #1337`. This tells GitHub to close the existing issue if the PR is merged.

.github/workflows/tests.yml

@@ -12,7 +12,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
-        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13", "3.14", "3.14t"]
+        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14", "3.14t"]
       fail-fast: false
 
     runs-on: ${{ matrix.os }}

.github/workflows/typecheck.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13", "3.14"]
+        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14"]
       fail-fast: false
     defaults:
       run:

.pre-commit-config.yaml

@@ -9,7 +9,7 @@ repos:
       - id: trailing-whitespace
 
   - repo: https://github.com/astral-sh/ruff-pre-commit
-    rev: "v0.12.4"
+    rev: "v0.12.7"
     hooks:
       - id: ruff-format
         args: [--config=pyproject.toml]
@@ -21,5 +21,5 @@ repos:
     hooks:
       - id: prettier
         additional_dependencies:
-          - prettier@3.5.3
-          - prettier-plugin-toml@2.0.5
+          - prettier@3.6.2
+          - prettier-plugin-toml@2.0.6

CHANGELOG.md

@@ -1,13 +1,12 @@
 ## 3.0.0 (TBD)
 
 - Breaking Changes
-
+    - `cmd2` 3.0 supports Python 3.10+ (removed support for Python 3.9)
     - No longer setting parser's `prog` value in `with_argparser()` since it gets set in
       `Cmd._build_parser()`. This code had previously been restored to support backward
       compatibility in `cmd2` 2.0 family.
 
 - Enhancements
-
     - Simplified the process to set a custom parser for `cmd2's` built-in commands. See
       [custom_parser.py](https://github.com/python-cmd2/cmd2/blob/main/examples/custom_parser.py)
       example for more details.
@@ -30,7 +29,6 @@
 ## 2.6.2 (June 26, 2025)
 
 - Enhancements
-
     - Added explicit support for free-threaded versions of Python, starting with version 3.14
 
 - Bug Fixes
@@ -1316,12 +1314,10 @@
 ## 0.8.5 (April 15, 2018)
 
 - Bug Fixes
-
     - Fixed a bug with all argument decorators where the wrapped function wasn't returning a value
       and thus couldn't cause the cmd2 app to quit
 
 - Enhancements
-
     - Added support for verbose help with -v where it lists a brief summary of what each command
       does
     - Added support for categorizing commands into groups within the help menu
@@ -1353,12 +1349,10 @@
 ## 0.8.3 (April 09, 2018)
 
 - Bug Fixes
-
     - Fixed `help` command not calling functions for help topics
     - Fixed not being able to use quoted paths when redirecting with `<` and `>`
 
 - Enhancements
-
     - Tab completion has been overhauled and now supports completion of strings with quotes and
       spaces.
     - Tab completion will automatically add an opening quote if a string with a space is completed.

README.md

@@ -87,7 +87,7 @@ On all operating systems, the latest stable version of `cmd2` can be installed u
 pip install -U cmd2
 ```
 
-cmd2 works with Python 3.9+ on Windows, macOS, and Linux. It is pure Python code with few 3rd-party
+cmd2 works with Python 3.10+ on Windows, macOS, and Linux. It is pure Python code with few 3rd-party
 dependencies. It works with both conventional CPython and free-threaded variants.
 
 For information on other installation options, see

cmd2/ansi.py

@@ -11,7 +11,6 @@
 from typing import (
     IO,
     Any,
-    Optional,
     cast,
 )
 
@@ -924,14 +923,14 @@ def __str__(self) -> str:
 def style(
     value: Any,
     *,
-    fg: Optional[FgColor] = None,
-    bg: Optional[BgColor] = None,
-    bold: Optional[bool] = None,
-    dim: Optional[bool] = None,
-    italic: Optional[bool] = None,
-    overline: Optional[bool] = None,
-    strikethrough: Optional[bool] = None,
-    underline: Optional[bool] = None,
+    fg: FgColor | None = None,
+    bg: BgColor | None = None,
+    bold: bool | None = None,
+    dim: bool | None = None,
+    italic: bool | None = None,
+    overline: bool | None = None,
+    strikethrough: bool | None = None,
+    underline: bool | None = None,
 ) -> str:
     """Apply ANSI colors and/or styles to a string and return it.
 

cmd2/argparse_completer.py

@@ -12,8 +12,6 @@
 from typing import (
     IO,
     TYPE_CHECKING,
-    Optional,
-    Union,
     cast,
 )
 
@@ -105,8 +103,8 @@ class _ArgumentState:
 
     def __init__(self, arg_action: argparse.Action) -> None:
         self.action = arg_action
-        self.min: Union[int, str]
-        self.max: Union[float, int, str]
+        self.min: int | str
+        self.max: float | int | str
         self.count = 0
         self.is_remainder = self.action.nargs == argparse.REMAINDER
 
@@ -141,7 +139,7 @@ def __init__(self, flag_arg_state: _ArgumentState) -> None:
         :param flag_arg_state: information about the unfinished flag action.
         """
         arg = f'{argparse._get_action_name(flag_arg_state.action)}'
-        err = f'{generate_range_error(cast(int, flag_arg_state.min), cast(Union[int, float], flag_arg_state.max))}'
+        err = f'{generate_range_error(cast(int, flag_arg_state.min), cast(int | float, flag_arg_state.max))}'
         error = f"Error: argument {arg}: {err} ({flag_arg_state.count} entered)"
         super().__init__(error)
 
@@ -163,7 +161,7 @@ class ArgparseCompleter:
     """Automatic command line tab completion based on argparse parameters."""
 
     def __init__(
-        self, parser: argparse.ArgumentParser, cmd2_app: 'Cmd', *, parent_tokens: Optional[dict[str, list[str]]] = None
+        self, parser: argparse.ArgumentParser, cmd2_app: 'Cmd', *, parent_tokens: dict[str, list[str]] | None = None
     ) -> None:
         """Create an ArgparseCompleter.
 
@@ -203,7 +201,7 @@ def __init__(
                     self._subcommand_action = action
 
     def complete(
-        self, text: str, line: str, begidx: int, endidx: int, tokens: list[str], *, cmd_set: Optional[CommandSet] = None
+        self, text: str, line: str, begidx: int, endidx: int, tokens: list[str], *, cmd_set: CommandSet | None = None
     ) -> list[str]:
         """Complete text using argparse metadata.
 
@@ -228,10 +226,10 @@ def complete(
         skip_remaining_flags = False
 
         # _ArgumentState of the current positional
-        pos_arg_state: Optional[_ArgumentState] = None
+        pos_arg_state: _ArgumentState | None = None
 
         # _ArgumentState of the current flag
-        flag_arg_state: Optional[_ArgumentState] = None
+        flag_arg_state: _ArgumentState | None = None
 
         # Non-reusable flags that we've parsed
         matched_flags: list[str] = []
@@ -523,7 +521,7 @@ def _complete_flags(self, text: str, line: str, begidx: int, endidx: int, matche
 
         return matches
 
-    def _format_completions(self, arg_state: _ArgumentState, completions: Union[list[str], list[CompletionItem]]) -> list[str]:
+    def _format_completions(self, arg_state: _ArgumentState, completions: list[str] | list[CompletionItem]) -> list[str]:
         """Format CompletionItems into hint table."""
         # Nothing to do if we don't have at least 2 completions which are all CompletionItems
         if len(completions) < 2 or not all(isinstance(c, CompletionItem) for c in completions):
@@ -625,7 +623,7 @@ def complete_subcommand_help(self, text: str, line: str, begidx: int, endidx: in
                 break
         return []
 
-    def print_help(self, tokens: list[str], file: Optional[IO[str]] = None) -> None:
+    def print_help(self, tokens: list[str], file: IO[str] | None = None) -> None:
         """Supports cmd2's help command in the printing of help text.
 
         :param tokens: arguments passed to help command
@@ -636,7 +634,7 @@ def print_help(self, tokens: list[str], file: Optional[IO[str]] = None) -> None:
         # If so, we will let the subcommand's parser handle the rest of the tokens via another ArgparseCompleter.
         if tokens and self._subcommand_action is not None:
             parser = cast(
-                Optional[argparse.ArgumentParser],
+                argparse.ArgumentParser | None,
                 self._subcommand_action.choices.get(tokens[0]),
             )
 
@@ -657,15 +655,15 @@ def _complete_arg(
         arg_state: _ArgumentState,
         consumed_arg_values: dict[str, list[str]],
         *,
-        cmd_set: Optional[CommandSet] = None,
+        cmd_set: CommandSet | None = None,
     ) -> list[str]:
         """Tab completion routine for an argparse argument.
 
         :return: list of completions
         :raises CompletionError: if the completer or choices function this calls raises one.
         """
         # Check if the arg provides choices to the user
-        arg_choices: Union[list[str], ChoicesCallable]
+        arg_choices: list[str] | ChoicesCallable
         if arg_state.action.choices is not None:
             arg_choices = list(arg_state.action.choices)
             if not arg_choices: