+def normalize_numeric_literal(leaf: Leaf, allow_underscores: bool) -> None:
+ """Normalizes numeric (float, int, and complex) literals.
+
+ All letters used in the representation are normalized to lowercase, long number
+ literals are split using underscores.
+ """
+ text = leaf.value.lower()
+ if text.startswith(("0o", "0x", "0b")):
+ # Leave octal, hex, and binary literals alone.
+ pass
+ elif "e" in text:
+ before, after = text.split("e")
+ sign = ""
+ if after.startswith("-"):
+ after = after[1:]
+ sign = "-"
+ elif after.startswith("+"):
+ after = after[1:]
+ before = format_float_or_int_string(before, allow_underscores)
+ after = format_int_string(after, allow_underscores)
+ text = f"{before}e{sign}{after}"
+ elif text.endswith(("j", "l")):
+ number = text[:-1]
+ suffix = text[-1]
+ text = f"{format_float_or_int_string(number, allow_underscores)}{suffix}"
+ else:
+ text = format_float_or_int_string(text, allow_underscores)
+ leaf.value = text
+
+
+def format_float_or_int_string(text: str, allow_underscores: bool) -> str:
+ """Formats a float string like "1.0"."""
+ if "." not in text:
+ return format_int_string(text, allow_underscores)
+
+ before, after = text.split(".")
+ before = format_int_string(before, allow_underscores) if before else "0"
+ after = format_int_string(after, allow_underscores) if after else "0"
+ return f"{before}.{after}"
+
+
+def format_int_string(text: str, allow_underscores: bool) -> str:
+ """Normalizes underscores in a string to e.g. 1_000_000.
+
+ Input must be a string of at least six digits and optional underscores.
+ """
+ if not allow_underscores:
+ return text
+
+ text = text.replace("_", "")
+ if len(text) <= 6:
+ # No underscores for numbers <= 6 digits long.
+ return text
+
+ return format(int(text), "3_")
+
+