MAINT Add pre-commit setup (#111)

Author: rth

.circleci/config.yml

@@ -13,7 +13,7 @@ jobs:
           command: |
               black --check examples sklearn_extra *py
               # ensure there is no unused imports with flake8
-              flake8 --select=F401
+              flake8
 
 workflows:
   version: 2

.pre-commit-config.yaml

@@ -0,0 +1,16 @@
+repos:
+-   repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v3.4.0
+    hooks:
+    -   id: check-yaml
+    -   id: end-of-file-fixer
+    -   id: trailing-whitespace
+-   repo: https://github.com/psf/black
+    rev: 20.8b1
+    hooks:
+    -   id: black
+-   repo: https://gitlab.com/pycqa/flake8
+    rev: 3.9.0
+    hooks:
+    -   id: flake8
+        types: [file, python]

doc/contributing.rst

@@ -37,7 +37,12 @@ This is still a very young project, but we do have a few guiding principles:
 2. Write detailed docstrings in numpy format
 3. Support pandas dataframes and numpy arrays as inputs
 4. Write tests
-5. Format with black
+5. Format with black. You can use `pre-commit <https://pre-commit.com/>`_ to auto-format code on each commit,
+
+   .. code-block:: console
+
+       pip install pre-commit
+       pre-commit install
 
 Running Tests
 ^^^^^^^^^^^^^

setup.cfg

@@ -7,3 +7,6 @@ test = pytest
 [tool:pytest]
 doctest_optionflags = NORMALIZE_WHITESPACE ELLIPSIS
 addopts = --doctest-modules
+
+[flake8]
+select = F401