From bc762428381fe2a02e3be997ad3291ea2cd331d7 Mon Sep 17 00:00:00 2001
From: Jon Meow <46229924+jonmeow@users.noreply.github.com>
Date: Mon, 29 Jun 2020 11:34:15 -0700
Subject: [PATCH] Configure black for Python formatting (#97)

---
 .pre-commit-config.yaml            | 7 ++++++-
 docs/project/contribution_tools.md | 9 +++++++++
 pyproject.toml                     | 4 ++++
 3 files changed, 19 insertions(+), 1 deletion(-)
 create mode 100644 pyproject.toml

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 782290432aae..c73ddb478170 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -31,7 +31,12 @@ repos:
         additional_dependencies: [markdown-toc]
         files: .*\.md$
         exclude: ^src/jekyll/theme/
-  # Prettier should be run late so that it can re-format any prior changes.
+  # Formatters should be run late so that they can re-format any prior changes.
+  - repo: https://github.com/psf/black
+    rev: stable
+    hooks:
+      - id: black
+        language_version: python3.6
   - repo: https://github.com/prettier/prettier
     rev: 2.0.5
     hooks:
diff --git a/docs/project/contribution_tools.md b/docs/project/contribution_tools.md
index e162ddaec602..2bd256eddf43 100644
--- a/docs/project/contribution_tools.md
+++ b/docs/project/contribution_tools.md
@@ -14,6 +14,7 @@ contributions.
 <!-- toc -->
 
 - [pre-commit](#pre-commit)
+- [black](#black)
 - [codespell](#codespell)
 - [markdown-toc](#markdown-toc)
 - [Prettier](#prettier)
@@ -42,6 +43,14 @@ To set up pre-commit:
 When modifying or adding pre-commit hooks, please run
 `pre-commit run --all-files` to see what changes.
 
+## black
+
+> **pre-commit enabled**: If you're using pre-commit, it will run this.
+> Installing and running manually is optional, but may be helpful.
+
+We use [Black](https://github.com/psf/black) to format Python code. Although
+[Prettier](#prettier) is used for most languages, it doesn't support Python.
+
 ## codespell
 
 > **pre-commit enabled**: If you're using pre-commit, it will run this.
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 000000000000..f30e22b74290
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,4 @@
+[tool.black]
+line-length = 80
+target-version = ['py36', 'py37', 'py38']
+include = '\.pyi?$'