From d4f05217546dd98f81ca472aa00e68d978c900f4 Mon Sep 17 00:00:00 2001
From: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Date: Mon, 20 Aug 2018 08:19:25 -0700
Subject: [PATCH] fix misformatting of floats with leading zeros (#464)

---
 black.py                       | 4 +++-
 tests/data/numeric_literals.py | 2 ++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/black.py b/black.py
index b65693e..5550b23 100644
--- a/black.py
+++ b/black.py
@@ -2564,7 +2564,9 @@ def format_int_string(text: str, allow_underscores: bool) -> str:
         # No underscores for numbers <= 6 digits long.
         return text
 
-    return format(int(text), "3_")
+    # Avoid removing leading zeros, which are important if we're formatting
+    # part of a number like "0.001".
+    return format(int("1" + text), "3_")[1:].lstrip("_")
 
 
 def normalize_invisible_parens(node: Node, parens_after: Set[str]) -> None:
diff --git a/tests/data/numeric_literals.py b/tests/data/numeric_literals.py
index 8999b9d..2dc64c7 100644
--- a/tests/data/numeric_literals.py
+++ b/tests/data/numeric_literals.py
@@ -14,6 +14,7 @@ x = 123456789.123456789J
 x = 0XB1ACC
 x = 0B1011
 x = 0O777
+x = 0.000000006
 
 # output
 
@@ -34,3 +35,4 @@ x = 123_456_789.123_456_789j
 x = 0xb1acc
 x = 0b1011
 x = 0o777
+x = 0.000_000_006
-- 
2.39.2