naturaldelta rounds the value to the nearest unit that makes sense

naturaldelta used to always round down. We want instead to round to the
nearest unit that makes sense.

fix #174

Author: Daniel Gillet

src/humanize/time.py

@@ -101,6 +101,8 @@ def naturaldelta(
 
     This is similar to `naturaltime`, but does not add tense to the result.
 
+    The timedelta will be rounded to the nearest unit that makes sense.
+
     Args:
         value (datetime.timedelta, int or float): A timedelta or a number of seconds.
         months (bool): If `True`, then a number of months (based on 30.5 days) will be
@@ -155,9 +157,9 @@ def naturaldelta(
     delta = abs(delta)
     years = delta.days // 365
     days = delta.days % 365
-    num_months = int(days // 30.5)
+    num_months = round(days / 30.5)
 
-    if not years and days < 1:
+    if years == 0 and days < 1:
         if delta.seconds == 0:
             if min_unit == Unit.MICROSECONDS and delta.microseconds < 1000:
                 return (
@@ -181,18 +183,24 @@ def naturaldelta(
         if delta.seconds < 60:
             return _ngettext("%d second", "%d seconds", delta.seconds) % delta.seconds
 
-        if 60 <= delta.seconds < 120:
-            return _("a minute")
+        if 60 <= delta.seconds < 3600:
+            minutes = round(delta.seconds / 60)
+            if minutes == 1:
+                return _("a minute")
+
+            if minutes == 60:
+                return _("an hour")
 
-        if 120 <= delta.seconds < 3600:
-            minutes = delta.seconds // 60
             return _ngettext("%d minute", "%d minutes", minutes) % minutes
 
-        if 3600 <= delta.seconds < 3600 * 2:
-            return _("an hour")
+        if 3600 <= delta.seconds:
+            hours = round(delta.seconds / 3600)
+            if hours == 1:
+                return _("an hour")
+
+            if hours == 24:
+                return _("a day")
 
-        if 3600 < delta.seconds:
-            hours = delta.seconds // 3600
             return _ngettext("%d hour", "%d hours", hours) % hours
 
     elif years == 0:
@@ -202,25 +210,32 @@ def naturaldelta(
         if not use_months:
             return _ngettext("%d day", "%d days", days) % days
 
-        if not num_months:
+        if num_months == 0:
             return _ngettext("%d day", "%d days", days) % days
 
         if num_months == 1:
             return _("a month")
 
+        if num_months == 12:
+            return _("a year")
+
         return _ngettext("%d month", "%d months", num_months) % num_months
 
     elif years == 1:
-        if not num_months and not days:
+        if num_months == 0 and days == 0:
             return _("a year")
 
-        if not num_months:
+        if num_months == 0:
             return _ngettext("1 year, %d day", "1 year, %d days", days) % days
 
         if use_months:
             if num_months == 1:
                 return _("1 year, 1 month")
 
+            if num_months == 12:
+                years += 1
+                return _ngettext("%d year", "%d years", years) % years
+
             return (
                 _ngettext("1 year, %d month", "1 year, %d months", num_months)
                 % num_months
@@ -242,6 +257,8 @@ def naturaltime(
 
     This is more or less compatible with Django's `naturaltime` filter.
 
+    The time will be rounded to the nearest unit that makes sense.
+
     Args:
         value (datetime.datetime, datetime.timedelta, int or float): A `datetime`, a
             `timedelta`, or a number of seconds.

tests/test_time.py

@@ -97,15 +97,26 @@ def test_naturaldelta_nomonths(test_input: dt.timedelta, expected: str) -> None:
         (23.5, "23 seconds"),
         (30, "30 seconds"),
         (dt.timedelta(microseconds=13), "a moment"),
-        (dt.timedelta(minutes=1, seconds=30), "a minute"),
+        (dt.timedelta(minutes=1, seconds=29), "a minute"),
+        (dt.timedelta(minutes=1, seconds=30), "2 minutes"),
+        (dt.timedelta(minutes=1, seconds=59), "2 minutes"),
         (dt.timedelta(minutes=2), "2 minutes"),
-        (dt.timedelta(hours=1, minutes=30, seconds=30), "an hour"),
-        (dt.timedelta(hours=23, minutes=50, seconds=50), "23 hours"),
+        (dt.timedelta(minutes=59), "59 minutes"),
+        (dt.timedelta(minutes=59, seconds=30), "an hour"),
+        (dt.timedelta(hours=1, minutes=29), "an hour"),
+        # Round to nearest, ties away from zero.
+        # See https://en.wikipedia.org/wiki/IEEE_754#Rounding_rules
+        (dt.timedelta(hours=1, minutes=30), "2 hours"),
+        (dt.timedelta(hours=2, minutes=30), "2 hours"),
+        (dt.timedelta(hours=3, minutes=30), "4 hours"),
+        (dt.timedelta(hours=23, minutes=50, seconds=50), "a day"),
         (dt.timedelta(days=1), "a day"),
         (dt.timedelta(days=500), "1 year, 4 months"),
         (dt.timedelta(days=365 * 2 + 35), "2 years"),
         (dt.timedelta(seconds=1), "a second"),
         (dt.timedelta(seconds=30), "30 seconds"),
+        (dt.timedelta(days=364), "a year"),
+        (dt.timedelta(days=365 + 364), "2 years"),
         # regression tests for bugs in post-release humanize
         (dt.timedelta(days=10000), "27 years"),
         (dt.timedelta(days=365 + 35), "1 year, 1 month"),
@@ -134,19 +145,25 @@ def test_naturaldelta(test_input: float | dt.timedelta, expected: str) -> None:
         (NOW, "now"),
         (NOW - dt.timedelta(seconds=1), "a second ago"),
         (NOW - dt.timedelta(seconds=30), "30 seconds ago"),
-        (NOW - dt.timedelta(minutes=1, seconds=30), "a minute ago"),
+        (NOW - dt.timedelta(minutes=1, seconds=29), "a minute ago"),
+        (NOW - dt.timedelta(minutes=1, seconds=30), "2 minutes ago"),
         (NOW - dt.timedelta(minutes=2), "2 minutes ago"),
-        (NOW - dt.timedelta(hours=1, minutes=30, seconds=30), "an hour ago"),
-        (NOW - dt.timedelta(hours=23, minutes=50, seconds=50), "23 hours ago"),
+        (NOW - dt.timedelta(hours=1, minutes=29, seconds=30), "an hour ago"),
+        (NOW - dt.timedelta(hours=1, minutes=30, seconds=30), "2 hours ago"),
+        (NOW - dt.timedelta(hours=23, minutes=29, seconds=50), "23 hours ago"),
+        (NOW - dt.timedelta(hours=23, minutes=50, seconds=50), "a day ago"),
         (NOW - dt.timedelta(days=1), "a day ago"),
         (NOW - dt.timedelta(days=500), "1 year, 4 months ago"),
         (NOW - dt.timedelta(days=365 * 2 + 35), "2 years ago"),
         (NOW + dt.timedelta(seconds=1), "a second from now"),
         (NOW + dt.timedelta(seconds=30), "30 seconds from now"),
-        (NOW + dt.timedelta(minutes=1, seconds=30), "a minute from now"),
+        (NOW + dt.timedelta(minutes=1, seconds=29), "a minute from now"),
+        (NOW + dt.timedelta(minutes=1, seconds=30), "2 minutes from now"),
         (NOW + dt.timedelta(minutes=2), "2 minutes from now"),
-        (NOW + dt.timedelta(hours=1, minutes=30, seconds=30), "an hour from now"),
-        (NOW + dt.timedelta(hours=23, minutes=50, seconds=50), "23 hours from now"),
+        (NOW + dt.timedelta(hours=1, minutes=29, seconds=30), "an hour from now"),
+        (NOW + dt.timedelta(hours=1, minutes=30, seconds=30), "2 hours from now"),
+        (NOW + dt.timedelta(hours=23, minutes=29, seconds=50), "23 hours from now"),
+        (NOW + dt.timedelta(hours=23, minutes=50, seconds=50), "a day from now"),
         (NOW + dt.timedelta(days=1), "a day from now"),
         (NOW + dt.timedelta(days=500), "1 year, 4 months from now"),
         (NOW + dt.timedelta(days=365 * 2 + 35), "2 years from now"),
@@ -156,6 +173,7 @@ def test_naturaldelta(test_input: float | dt.timedelta, expected: str) -> None:
         (dt.timedelta(days=-10000), "27 years from now"),
         (dt.timedelta(days=365 + 35), "1 year, 1 month ago"),
         (23.5, "23 seconds ago"),
+        # (23.9, "24 seconds ago"),
         (30, "30 seconds ago"),
         (NOW - dt.timedelta(days=365 * 2 + 65), "2 years ago"),
         (NOW - dt.timedelta(days=365 + 4), "1 year, 4 days ago"),
@@ -175,21 +193,26 @@ def test_naturaltime(
         (NOW, "now"),
         (NOW - dt.timedelta(seconds=1), "a second ago"),
         (NOW - dt.timedelta(seconds=30), "30 seconds ago"),
-        (NOW - dt.timedelta(minutes=1, seconds=30), "a minute ago"),
+        (NOW - dt.timedelta(minutes=1, seconds=29), "a minute ago"),
+        (NOW - dt.timedelta(minutes=1, seconds=30), "2 minutes ago"),
         (NOW - dt.timedelta(minutes=2), "2 minutes ago"),
-        (NOW - dt.timedelta(hours=1, minutes=30, seconds=30), "an hour ago"),
-        (NOW - dt.timedelta(hours=23, minutes=50, seconds=50), "23 hours ago"),
+        (NOW - dt.timedelta(hours=1, minutes=29, seconds=30), "an hour ago"),
+        (NOW - dt.timedelta(hours=1, minutes=30, seconds=30), "2 hours ago"),
+        (NOW - dt.timedelta(hours=23, minutes=50, seconds=50), "a day ago"),
         (NOW - dt.timedelta(days=1), "a day ago"),
         (NOW - dt.timedelta(days=17), "17 days ago"),
         (NOW - dt.timedelta(days=47), "47 days ago"),
         (NOW - dt.timedelta(days=500), "1 year, 135 days ago"),
         (NOW - dt.timedelta(days=365 * 2 + 35), "2 years ago"),
         (NOW + dt.timedelta(seconds=1), "a second from now"),
         (NOW + dt.timedelta(seconds=30), "30 seconds from now"),
-        (NOW + dt.timedelta(minutes=1, seconds=30), "a minute from now"),
+        (NOW + dt.timedelta(minutes=1, seconds=29), "a minute from now"),
+        (NOW + dt.timedelta(minutes=1, seconds=30), "2 minutes from now"),
         (NOW + dt.timedelta(minutes=2), "2 minutes from now"),
-        (NOW + dt.timedelta(hours=1, minutes=30, seconds=30), "an hour from now"),
-        (NOW + dt.timedelta(hours=23, minutes=50, seconds=50), "23 hours from now"),
+        (NOW + dt.timedelta(hours=1, minutes=29, seconds=30), "an hour from now"),
+        (NOW + dt.timedelta(hours=1, minutes=30, seconds=30), "2 hours from now"),
+        (NOW + dt.timedelta(hours=23, minutes=29, seconds=50), "23 hours from now"),
+        (NOW + dt.timedelta(hours=23, minutes=50, seconds=50), "a day from now"),
         (NOW + dt.timedelta(days=1), "a day from now"),
         (NOW + dt.timedelta(days=500), "1 year, 135 days from now"),
         (NOW + dt.timedelta(days=365 * 2 + 35), "2 years from now"),
@@ -419,19 +442,25 @@ def test_naturaltime_minimum_unit_explicit(
         (NOW_UTC, "now"),
         (NOW_UTC - dt.timedelta(seconds=1), "a second ago"),
         (NOW_UTC - dt.timedelta(seconds=30), "30 seconds ago"),
-        (NOW_UTC - dt.timedelta(minutes=1, seconds=30), "a minute ago"),
+        (NOW_UTC - dt.timedelta(minutes=1, seconds=29), "a minute ago"),
+        (NOW_UTC - dt.timedelta(minutes=1, seconds=30), "2 minutes ago"),
         (NOW_UTC - dt.timedelta(minutes=2), "2 minutes ago"),
-        (NOW_UTC - dt.timedelta(hours=1, minutes=30, seconds=30), "an hour ago"),
-        (NOW_UTC - dt.timedelta(hours=23, minutes=50, seconds=50), "23 hours ago"),
+        (NOW_UTC - dt.timedelta(hours=1, minutes=29, seconds=30), "an hour ago"),
+        (NOW_UTC - dt.timedelta(hours=1, minutes=30, seconds=30), "2 hours ago"),
+        (NOW_UTC - dt.timedelta(hours=23, minutes=29, seconds=50), "23 hours ago"),
+        (NOW_UTC - dt.timedelta(hours=23, minutes=50, seconds=50), "a day ago"),
         (NOW_UTC - dt.timedelta(days=1), "a day ago"),
         (NOW_UTC - dt.timedelta(days=500), "1 year, 4 months ago"),
         (NOW_UTC - dt.timedelta(days=365 * 2 + 35), "2 years ago"),
         (NOW_UTC + dt.timedelta(seconds=1), "a second from now"),
         (NOW_UTC + dt.timedelta(seconds=30), "30 seconds from now"),
-        (NOW_UTC + dt.timedelta(minutes=1, seconds=30), "a minute from now"),
+        (NOW_UTC + dt.timedelta(minutes=1, seconds=29), "a minute from now"),
+        (NOW_UTC + dt.timedelta(minutes=1, seconds=30), "2 minutes from now"),
         (NOW_UTC + dt.timedelta(minutes=2), "2 minutes from now"),
-        (NOW_UTC + dt.timedelta(hours=1, minutes=30, seconds=30), "an hour from now"),
-        (NOW_UTC + dt.timedelta(hours=23, minutes=50, seconds=50), "23 hours from now"),
+        (NOW_UTC + dt.timedelta(hours=1, minutes=29, seconds=30), "an hour from now"),
+        (NOW_UTC + dt.timedelta(hours=1, minutes=30, seconds=30), "2 hours from now"),
+        (NOW_UTC + dt.timedelta(hours=23, minutes=29, seconds=50), "23 hours from now"),
+        (NOW_UTC + dt.timedelta(hours=23, minutes=50, seconds=50), "a day from now"),
         (NOW_UTC + dt.timedelta(days=1), "a day from now"),
         (NOW_UTC + dt.timedelta(days=500), "1 year, 4 months from now"),
         (NOW_UTC + dt.timedelta(days=365 * 2 + 35), "2 years from now"),
@@ -453,19 +482,25 @@ def test_naturaltime_timezone(test_input: dt.datetime, expected: str) -> None:
         (NOW_UTC, "now"),
         (NOW_UTC - dt.timedelta(seconds=1), "a second ago"),
         (NOW_UTC - dt.timedelta(seconds=30), "30 seconds ago"),
-        (NOW_UTC - dt.timedelta(minutes=1, seconds=30), "a minute ago"),
+        (NOW_UTC - dt.timedelta(minutes=1, seconds=29), "a minute ago"),
+        (NOW_UTC - dt.timedelta(minutes=1, seconds=30), "2 minutes ago"),
         (NOW_UTC - dt.timedelta(minutes=2), "2 minutes ago"),
-        (NOW_UTC - dt.timedelta(hours=1, minutes=30, seconds=30), "an hour ago"),
-        (NOW_UTC - dt.timedelta(hours=23, minutes=50, seconds=50), "23 hours ago"),
+        (NOW_UTC - dt.timedelta(hours=1, minutes=29, seconds=30), "an hour ago"),
+        (NOW_UTC - dt.timedelta(hours=1, minutes=30, seconds=30), "2 hours ago"),
+        (NOW_UTC - dt.timedelta(hours=23, minutes=29, seconds=50), "23 hours ago"),
+        (NOW_UTC - dt.timedelta(hours=23, minutes=50, seconds=50), "a day ago"),
         (NOW_UTC - dt.timedelta(days=1), "a day ago"),
         (NOW_UTC - dt.timedelta(days=500), "1 year, 4 months ago"),
         (NOW_UTC - dt.timedelta(days=365 * 2 + 35), "2 years ago"),
         (NOW_UTC + dt.timedelta(seconds=1), "a second from now"),
         (NOW_UTC + dt.timedelta(seconds=30), "30 seconds from now"),
-        (NOW_UTC + dt.timedelta(minutes=1, seconds=30), "a minute from now"),
+        (NOW_UTC + dt.timedelta(minutes=1, seconds=29), "a minute from now"),
+        (NOW_UTC + dt.timedelta(minutes=1, seconds=30), "2 minutes from now"),
         (NOW_UTC + dt.timedelta(minutes=2), "2 minutes from now"),
-        (NOW_UTC + dt.timedelta(hours=1, minutes=30, seconds=30), "an hour from now"),
-        (NOW_UTC + dt.timedelta(hours=23, minutes=50, seconds=50), "23 hours from now"),
+        (NOW_UTC + dt.timedelta(hours=1, minutes=29, seconds=30), "an hour from now"),
+        (NOW_UTC + dt.timedelta(hours=1, minutes=30, seconds=30), "2 hours from now"),
+        (NOW_UTC + dt.timedelta(hours=23, minutes=29, seconds=50), "23 hours from now"),
+        (NOW_UTC + dt.timedelta(hours=23, minutes=50, seconds=50), "a day from now"),
         (NOW_UTC + dt.timedelta(days=1), "a day from now"),
         (NOW_UTC + dt.timedelta(days=500), "1 year, 4 months from now"),
         (NOW_UTC + dt.timedelta(days=365 * 2 + 35), "2 years from now"),