Return NaN/Inf unchanged from naturalsize()

src/humanize/filesize.py

@@ -2,11 +2,17 @@
 
 from __future__ import annotations
 
-__lazy_modules__ = {"humanize.i18n", "math"}
+__lazy_modules__ = {"humanize.i18n", "humanize.number", "math"}
 
-from math import log
+from math import isfinite, log
 
+# Import isfinite so we can check whether a number is
+# a normal finite number or NaN / positive infinity / negative infinity.
+# Reuse the existing helper from number.py so that
+# naturalsize() behaves consistently with other numeric
+# humanization functions in the library.
 from humanize.i18n import _gettext as _
+from humanize.number import _format_not_finite
 
 suffixes = {
     "decimal": (
@@ -92,6 +98,10 @@ def naturalsize(
     bytes_ = float(value)
     abs_bytes = abs(bytes_)
 
+    # Handle NaN and infinity before filesize formatting.
+    if not isfinite(bytes_):
+        return _format_not_finite(bytes_)
+
     if abs_bytes == 1 and not gnu:
         return _("%d Byte") % int(bytes_)
 

tests/test_filesize.py

@@ -4,6 +4,8 @@
 
 from __future__ import annotations
 
+import math
+
 import pytest
 
 import humanize
@@ -95,11 +97,24 @@
 )
 def test_naturalsize(test_args: list[int] | list[int | bool], expected: str) -> None:
     assert humanize.naturalsize(*test_args) == expected
-
     # Retest with negative input
     if isinstance(test_args[0], int):
         test_args[0] *= -1
     else:
         test_args[0] = f"-{test_args[0]}"
 
     assert humanize.naturalsize(*test_args) == "-" + expected
+
+
+@pytest.mark.parametrize(
+    "test_input, expected",
+    [
+        (math.nan, "NaN"),
+        (math.inf, "+Inf"),
+        (-math.inf, "-Inf"),
+    ],
+)
+def test_naturalsize_not_finite(test_input: float, expected: str) -> None:
+    assert humanize.naturalsize(test_input) == expected
+    assert humanize.naturalsize(test_input, binary=True) == expected
+    assert humanize.naturalsize(test_input, gnu=True) == expected