diff --git a/makefile b/makefile
--- a/makefile
+++ b/makefile
@@ -56,6 +56,9 @@ mypy-collector:
 mypy-paint:
 	env/bin/mypy --ignore-missing-imports --strict-optional --custom-typeshed-dir stubs --html-report /tmp/rep light9/paint/*.py
 
+reformat:
+	env/bin/yapf --verbose --parallel --in-place --style google light9/**/*.py `file --no-pad  bin/* | grep 'Python script' | perl -lpe 's/:.*//'`
+
 ### show ###
 
 darcs_show_checkpoint:
diff --git a/requirements.txt b/requirements.txt
--- a/requirements.txt
+++ b/requirements.txt
@@ -28,6 +28,7 @@ txzmq==0.8.0
 typing==3.6.1
 watchdog==0.8.3
 webcolors==1.7
+yapf==0.27.0
 
 git+http://github.com/drewp/scales.git@448d59fb491b7631877528e7695a93553bfaaa93#egg=scales
 git+http://github.com/11craft/louie.git@f18bb71010c114eca9c6b88c96453340e3b39454#egg=louie