Fix naturaldelta sub second precision (#169)

src/humanize/time.py

@@ -105,7 +105,8 @@ def naturaldelta(
     Returns:
         str (str or `value`): A natural representation of the amount of time
             elapsed unless `value` is not datetime.timedelta or cannot be
-            converted to int. In that case, a `value` is returned unchanged.
+            converted to int (cannot be float due to 'inf' or 'nan').
+            In that case, a `value` is returned unchanged.
 
     Raises:
         OverflowError: If `value` is too large to convert to datetime.timedelta.
@@ -132,7 +133,8 @@ def naturaldelta(
         delta = value
     else:
         try:
-            value = int(value)
+            int(value)  # Explicitly don't support string such as "NaN" or "inf"
+            value = float(value)
             delta = dt.timedelta(seconds=value)
         except (ValueError, TypeError):
             return str(value)

tests/test_time.py

@@ -127,7 +127,7 @@ def test_naturaldelta_nomonths(test_input: dt.timedelta, expected: str) -> None:
         (dt.timedelta(days=999_999_999), "2,739,726 years"),
     ],
 )
-def test_naturaldelta(test_input: int | dt.timedelta, expected: str) -> None:
+def test_naturaldelta(test_input: float | dt.timedelta, expected: str) -> None:
     assert humanize.naturaldelta(test_input) == expected
 
 
@@ -340,6 +340,7 @@ def test_naturaldelta_minimum_unit_explicit(
 
     # Act / Assert
     assert humanize.naturaldelta(delta, minimum_unit=minimum_unit) == expected
+    assert humanize.naturaldelta(seconds, minimum_unit=minimum_unit) == expected
 
 
 @freeze_time("2020-02-02")