Drop support for EOL Python 3.9

.flake8

@@ -1,6 +1,5 @@
 [flake8]
-# B905 should be enabled when we drop support for 3.9
-ignore = E203, E266, E501, E701, E704, W503, B905, B907
+ignore = E203, E266, E501, E701, E704, W503, B907
 # line length is intentionally set to 80 here because black uses Bugbear
 # See https://black.readthedocs.io/en/stable/guides/using_black_with_other_tools.html#bugbear for more details
 max-line-length = 80

.github/ISSUE_TEMPLATE/bug_report.md

@@ -41,7 +41,7 @@ this = "code"
 And run it with these arguments:
 
 ```sh
-$ black file.py --target-version py39
+$ black file.py --target-version py310
 ```
 
 The resulting error is:

.github/workflows/fuzz.yml

@@ -22,7 +22,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.9", "3.10", "3.11", "3.12.4", "3.13", "3.14"]
+        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14"]
 
     steps:
       - uses: actions/checkout@v5

.github/workflows/pypi_upload.yml

@@ -75,7 +75,7 @@ jobs:
           github.event_name == 'pull_request' && !contains(github.event.pull_request.labels.*.name, 'ci: build all wheels')
         run: |
           {
-            CIBW_BUILD="cp39-*" cibuildwheel --print-build-identifiers --platform linux | pyp 'json.dumps({"only": x, "os": "ubuntu-latest"})'
+            CIBW_BUILD="cp310-*" cibuildwheel --print-build-identifiers --platform linux | pyp 'json.dumps({"only": x, "os": "ubuntu-latest"})'
             CIBW_BUILD="cp314-*" cibuildwheel --print-build-identifiers --platform windows | pyp 'json.dumps({"only": x, "os": "windows-latest"})'
           } | pyp 'json.dumps(list(map(json.loads, lines)))' > /tmp/matrix
         env:

.github/workflows/test.yml

@@ -31,16 +31,14 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.9", "3.10", "3.11", "3.12.10", "3.13", "3.14", "pypy-3.9"]
+        python-version: ["3.10", "3.11", "3.12.10", "3.13", "3.14", "pypy-3.11"]
         os: [ubuntu-latest, macOS-latest, windows-latest, windows-11-arm]
         exclude:
-          # setup-python only supports 3.11+ on arm64 windows
-          - os: windows-11-arm
-            python-version: "3.9"
+          # setup-python only supports CPython 3.11+ on arm64 windows
           - os: windows-11-arm
             python-version: "3.10"
           - os: windows-11-arm
-            python-version: "pypy-3.9"
+            python-version: "pypy-3.11"
 
     steps:
       - uses: actions/checkout@v5

CHANGES.md

@@ -9,6 +9,8 @@
 
 <!-- Include any especially major or disruptive changes here -->
 
+- Black no longer supports running with Python 3.9 (#4842)
+
 ### Stable style
 
 <!-- Changes that affect Black's stable style -->

README.md

@@ -39,8 +39,9 @@ Try it out now using the [Black Playground](https://black.vercel.app). Watch the
 
 ### Installation
 
-_Black_ can be installed by running `pip install black`. It requires Python 3.9+ to run.
-If you want to format Jupyter Notebooks, install with `pip install "black[jupyter]"`.
+_Black_ can be installed by running `pip install black`. It requires Python 3.10+ to
+run. If you want to format Jupyter Notebooks, install with
+`pip install "black[jupyter]"`.
 
 ### Usage
 

action/main.py

@@ -5,7 +5,6 @@
 import sys
 from pathlib import Path
 from subprocess import PIPE, STDOUT, run
-from typing import Union
 
 ACTION_PATH = Path(os.environ["GITHUB_ACTION_PATH"])
 ENV_PATH = ACTION_PATH / ".black-env"
@@ -95,7 +94,7 @@ def read_version_specifier_from_pyproject() -> str:
     return version
 
 
-def find_black_version_in_array(array: object) -> Union[str, None]:
+def find_black_version_in_array(array: object) -> str | None:
     if not isinstance(array, list):
         return None
     try:

autoload/black.vim

@@ -84,8 +84,8 @@ def _initialize_black_env(upgrade=False):
       return True
 
   pyver = sys.version_info[:3]
-  if pyver < (3, 9):
-    print("Sorry, Black requires Python 3.9+ to run.")
+  if pyver < (3, 10):
+    print("Sorry, Black requires Python 3.10+ to run.")
     return False
 
   from pathlib import Path

docs/contributing/the_basics.md

@@ -53,7 +53,7 @@ Further examples of invoking the tests
 (.venv)$ tox --parallel=auto
 
 # Run tests on a specific python version
-(.venv)$ tox -e py39
+(.venv)$ tox -e py314
 
 # Run an individual test
 (.venv)$ pytest -k <test name>

docs/getting_started.md

@@ -16,8 +16,9 @@ Also, you can try out _Black_ online for minimal fuss on the
 
 ## Installation
 
-_Black_ can be installed by running `pip install black`. It requires Python 3.9+ to run.
-If you want to format Jupyter Notebooks, install with `pip install "black[jupyter]"`.
+_Black_ can be installed by running `pip install black`. It requires Python 3.10+ to
+run. If you want to format Jupyter Notebooks, install with
+`pip install "black[jupyter]"`.
 
 If you use pipx, you can install Black with `pipx install black`.
 

docs/integrations/editors.md

@@ -232,8 +232,8 @@ Configuration:
 
 #### Installation
 
-This plugin **requires Vim 7.0+ built with Python 3.9+ support**. It needs Python 3.9 to
-be able to run _Black_ inside the Vim process which is much faster than calling an
+This plugin **requires Vim 7.0+ built with Python 3.10+ support**. It needs Python 3.10
+to be able to run _Black_ inside the Vim process which is much faster than calling an
 external command.
 
 ##### `vim-plug`

gallery/gallery.py

@@ -11,7 +11,7 @@
 from concurrent.futures import ThreadPoolExecutor
 from functools import lru_cache, partial
 from pathlib import Path
-from typing import NamedTuple, Optional, Union, cast
+from typing import NamedTuple, Union, cast
 from urllib.request import urlopen, urlretrieve
 
 PYPI_INSTANCE = "https://pypi.org/pypi"
@@ -28,10 +28,10 @@
 
 class BlackVersion(NamedTuple):
     version: str
-    config: Optional[str] = None
+    config: str | None = None
 
 
-def get_pypi_download_url(package: str, version: Optional[str]) -> str:
+def get_pypi_download_url(package: str, version: str | None) -> str:
     with urlopen(PYPI_INSTANCE + f"/{package}/json") as page:
         metadata = json.load(page)
 
@@ -62,7 +62,7 @@ def get_top_packages() -> list[str]:
     return [package["project"] for package in result["rows"]]
 
 
-def get_package_source(package: str, version: Optional[str]) -> str:
+def get_package_source(package: str, version: str | None) -> str:
     if package == "cpython":
         if version is None:
             version = "main"
@@ -93,7 +93,7 @@ def get_first_archive_member(archive: ArchiveKind) -> str:
         return archive.namelist()[0]
 
 
-def download_and_extract(package: str, version: Optional[str], directory: Path) -> Path:
+def download_and_extract(package: str, version: str | None, directory: Path) -> Path:
     source = get_package_source(package, version)
 
     local_file, _ = urlretrieve(source, directory / f"{package}-src")
@@ -104,8 +104,8 @@ def download_and_extract(package: str, version: Optional[str], directory: Path)
 
 
 def get_package(
-    package: str, version: Optional[str], directory: Path
-) -> Optional[Path]:
+    package: str, version: str | None, directory: Path
+) -> Path | None:
     try:
         return download_and_extract(package, version, directory)
     except Exception:
@@ -140,7 +140,7 @@ def git_add_and_commit(msg: str, repo: Path) -> None:
 
 
 def git_switch_branch(
-    branch: str, repo: Path, new: bool = False, from_branch: Optional[str] = None
+    branch: str, repo: Path, new: bool = False, from_branch: str | None = None
 ) -> None:
     args = ["git", "checkout"]
     if new:
@@ -198,7 +198,7 @@ def black_runner(version: str, black_repo: Path) -> Path:
 
 def format_repo_with_version(
     repo: Path,
-    from_branch: Optional[str],
+    from_branch: str | None,
     black_repo: Path,
     black_version: BlackVersion,
     input_directory: Path,
@@ -207,7 +207,7 @@ def format_repo_with_version(
     git_switch_branch(black_version.version, repo=black_repo)
     git_switch_branch(current_branch, repo=repo, new=True, from_branch=from_branch)
 
-    format_cmd: list[Union[Path, str]] = [
+    format_cmd: list[Path | str] = [
         black_runner(black_version.version, black_repo),
         (black_repo / "black.py").resolve(),
         ".",

plugin/black.vim

@@ -27,7 +27,7 @@ if v:version < 700 || !has('python3')
           call add(messages, "vim7.0+")
         endif
         if !has('python3')
-          call add(messages, "Python 3.9 support")
+          call add(messages, "Python 3.10 support")
         endif
 
         echo "The black.vim plugin requires" join(messages, " and ")
@@ -81,11 +81,11 @@ endif
 
 function BlackComplete(ArgLead, CmdLine, CursorPos)
   return [
-\    'target_version=py39',
 \    'target_version=py310',
 \    'target_version=py311',
 \    'target_version=py312',
 \    'target_version=py313',
+\    'target_version=py314',
 \  ]
 endfunction
 

pyproject.toml

@@ -7,7 +7,7 @@
 
 [tool.black]
 line-length = 88
-target-version = ['py39']
+target-version = ['py310']
 include = '\.pyi?$'
 extend-exclude = '''
 /(
@@ -35,7 +35,7 @@ name = "black"
 description = "The uncompromising code formatter."
 license = "MIT"
 license-files = ["LICENSE"]
-requires-python = ">=3.9"
+requires-python = ">=3.10"
 authors = [
   { name = "Łukasz Langa", email = "lukasz@langa.pl" },
 ]
@@ -55,7 +55,6 @@ classifiers = [
   "Operating System :: OS Independent",
   "Programming Language :: Python",
   "Programming Language :: Python :: 3 :: Only",
-  "Programming Language :: Python :: 3.9",
   "Programming Language :: Python :: 3.10",
   "Programming Language :: Python :: 3.11",
   "Programming Language :: Python :: 3.12",
@@ -153,10 +152,10 @@ options = { debug_level = "0" }
 build-verbosity = 1
 
 # So these are the environments we target:
-# - Python: CPython 3.9+ only
+# - Python: CPython 3.10+ only
 # - Architecture (64-bit only): amd64 / x86_64, universal2, and arm64
 # - OS: Linux (no musl), Windows, and macOS
-build = "cp3*"
+build = "cp31*"
 skip = [
     "*-manylinux_i686",
     "*-musllinux_*",
@@ -229,7 +228,7 @@ branch = true
 # Specify the target platform details in config, so your developers are
 # free to run mypy on Windows, Linux, or macOS and get consistent
 # results.
-python_version = "3.9"
+python_version = "3.10"
 mypy_path = "src"
 strict = true
 strict_bytes = true

scripts/check_pre_commit_rev_in_example.py

@@ -21,9 +21,9 @@ def main(changes: str, source_version_control: str) -> None:
     changes_html = commonmark.commonmark(changes)
     changes_soup = BeautifulSoup(changes_html, "html.parser")
     headers = changes_soup.find_all("h2")
-    latest_tag, *_ = [
+    latest_tag, *_ = (
         header.string for header in headers if header.string != "Unreleased"
-    ]
+    )
 
     source_version_control_html = commonmark.commonmark(source_version_control)
     source_version_control_soup = BeautifulSoup(

scripts/migrate-black.py

@@ -40,7 +40,7 @@ def blackify(base_branch: str, black_command: str, logger: logging.Logger) -> in
 
     git("checkout", base_branch, f"-b{current_branch}-black")
 
-    for last_commit, commit in zip(commits, commits[1:]):
+    for last_commit, commit in zip(commits, commits[1:], strict=False):
         allow_empty = (
             b"--allow-empty" in run(["git", "apply", "-h"], stdout=PIPE).stdout
         )