diff --git a/.gitignore b/.gitignore
index ccead16..798dffa 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
 bitcoin_*.png
 bitcoin_*.txt
 /output
+scratch.py
diff --git a/justfile b/justfile
index 14c4c8c..d7ea2da 100644
--- a/justfile
+++ b/justfile
@@ -7,5 +7,8 @@ run *name:
         mv bitcoin_*.png bitcoin_*.txt "${OUT_DIR}"; \
     fi
 
+fmt:
+    black ./*.py
+
 clean:
     rm -f bitcoin_*.png bitcoin_*.txt