fix misformatting of floats with leading zeros (#464)

diff --git a/black.py b/black.py
index b65693e91d0cac0b5087b32397f22c64cee1b5e0..5550b23102025e4e11dc1a4bfe4fda2b7a1c3d83 100644 (file)
--- 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 8999b9d403830f3baa7e641a420f35663ae07ad5..2dc64c75c8b7c07ccb9d5aadb215023af6f2c7b8 100644 (file)
--- 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