CI: add pre-commit action, include pyupgrade

.github/workflows/pre-commit.yml

@@ -0,0 +1,14 @@
+name: pre-commit
+
+on:
+  pull_request:
+  push:
+    branches: [master]
+
+jobs:
+  pre-commit:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions/setup-python@v2
+    - uses: pre-commit/action@v2.0.0

.pre-commit-config.yaml

@@ -3,30 +3,30 @@ repos:
     rev: 19.10b0
     hooks:
     -   id: black
-        language_version: python3
 -   repo: https://gitlab.com/pycqa/flake8
     rev: 3.8.3
     hooks:
     -   id: flake8
-        language: python_venv
         additional_dependencies: [flake8-comprehensions>=3.1.0]
     -   id: flake8
         name: flake8-pyx
-        language: python_venv
         files: \.(pyx|pxd)$
         types:
           - file
         args: [--append-config=flake8/cython.cfg]
     -   id: flake8
         name: flake8-pxd
-        language: python_venv
         files: \.pxi\.in$
         types:
           - file
         args: [--append-config=flake8/cython-template.cfg]
--   repo: https://github.com/pre-commit/mirrors-isort
-    rev: v5.2.2
+-   repo: https://github.com/PyCQA/isort
+    rev: 5.2.2
     hooks:
     -   id: isort
-        language: python_venv
         exclude: ^pandas/__init__\.py$|^pandas/core/api\.py$
+-   repo: https://github.com/asottile/pyupgrade
+    rev: v2.7.2
+    hooks:
+    -   id: pyupgrade
+        args: [--py37-plus]

doc/source/development/contributing.rst

@@ -634,6 +634,10 @@ do not make sudden changes to the code that could have the potential to break
 a lot of user code as a result, that is, we need it to be as *backwards compatible*
 as possible to avoid mass breakages.
 
+In addition to ``./ci/code_checks.sh``, some extra checks are run by
+``pre-commit`` - see :ref:`here <contributing.pre-commit>` for how to
+run them.
+
 Additional standards are outlined on the :ref:`pandas code style guide <code_style>`
 
 Optional dependencies
@@ -826,6 +830,13 @@ remain up-to-date with our code checks as they change.
 
 Note that if needed, you can skip these checks with ``git commit --no-verify``.
 
+If you don't want to use ``pre-commit`` as part of your workflow, you can still use it
+to run its checks by running::
+
+    pre-commit run --files <files you have modified>
+
+without having to have done ``pre-commit install`` beforehand.
+
 Backwards compatibility
 ~~~~~~~~~~~~~~~~~~~~~~~
 

doc/sphinxext/announce.py

@@ -1,5 +1,4 @@
 #!/usr/bin/env python3
-# -*- encoding:utf-8 -*-
 """
 Script to generate contributor and pull request lists
 

environment.yml

@@ -22,7 +22,9 @@ dependencies:
   - flake8-rst>=0.6.0,<=0.7.0  # linting of code blocks in rst files
   - isort>=5.2.1  # check that imports are in the right order
   - mypy=0.782
+  - pre-commit
   - pycodestyle  # used by flake8
+  - pyupgrade
 
   # documentation
   - gitpython  # obtain contributors from git for whatsnew

requirements-dev.txt

@@ -13,7 +13,9 @@ flake8-comprehensions>=3.1.0
 flake8-rst>=0.6.0,<=0.7.0
 isort>=5.2.1
 mypy==0.782
+pre-commit
 pycodestyle
+pyupgrade
 gitpython
 gitdb
 sphinx