remove the ability of datetime.time to be considered false (closes #13936)

Doc/library/datetime.rst

@@ -1378,10 +1378,13 @@ Supported operations:
 
 * efficient pickling
 
-* in Boolean contexts, a :class:`.time` object is considered to be true if and
-  only if, after converting it to minutes and subtracting :meth:`utcoffset` (or
-  ``0`` if that's ``None``), the result is non-zero.
+In boolean contexts, a :class:`.time` object is always considered to be true.
 
+.. versionchanged:: 3.5
+   Before Python 3.5, a :class:`.time` object was considered to be false if it
+   represented midnight in UTC.  This behavior was considered obscure and
+   error-prone and has been removed in Python 3.5.  See :issue:`13936` for full
+   details.
 
 Instance methods:
 

Doc/whatsnew/3.5.rst

@@ -186,4 +186,7 @@ Porting to Python 3.5
 This section lists previously described changes and other bugfixes
 that may require changes to your code.
 
-* Nothing yet.
+* Before Python 3.5, a :class:`datetime.time` object was considered to be false
+  if it represented midnight in UTC.  This behavior was considered obscure and
+  error-prone and has been removed in Python 3.5.  See :issue:`13936` for full
+  details.

Lib/datetime.py

@@ -1249,12 +1249,6 @@ class time:
         _check_tzinfo_arg(tzinfo)
         return time(hour, minute, second, microsecond, tzinfo)
 
-    def __bool__(self):
-        if self.second or self.microsecond:
-            return True
-        offset = self.utcoffset() or timedelta(0)
-        return timedelta(hours=self.hour, minutes=self.minute) != offset
-
     # Pickle support.
 
     def _getstate(self):

Lib/test/datetimetester.py

@@ -2270,13 +2270,14 @@ class TestTime(HarmlessMixedComparison, unittest.TestCase):
             self.assertEqual(orig, derived)
 
     def test_bool(self):
+        # time is always True.
         cls = self.theclass
         self.assertTrue(cls(1))
         self.assertTrue(cls(0, 1))
         self.assertTrue(cls(0, 0, 1))
         self.assertTrue(cls(0, 0, 0, 1))
-        self.assertFalse(cls(0))
-        self.assertFalse(cls())
+        self.assertTrue(cls(0))
+        self.assertTrue(cls())
 
     def test_replace(self):
         cls = self.theclass
@@ -2629,7 +2630,7 @@ class TestTimeTZ(TestTime, TZInfoBase, unittest.TestCase):
             self.assertEqual(derived.tzname(), 'cookie')
 
     def test_more_bool(self):
-        # Test cases with non-None tzinfo.
+        # time is always True.
         cls = self.theclass
 
         t = cls(0, tzinfo=FixedOffset(-300, ""))
@@ -2639,23 +2640,11 @@ class TestTimeTZ(TestTime, TZInfoBase, unittest.TestCase):
         self.assertTrue(t)
 
         t = cls(5, tzinfo=FixedOffset(300, ""))
-        self.assertFalse(t)
+        self.assertTrue(t)
 
         t = cls(23, 59, tzinfo=FixedOffset(23*60 + 59, ""))
-        self.assertFalse(t)
-
-        # Mostly ensuring this doesn't overflow internally.
-        t = cls(0, tzinfo=FixedOffset(23*60 + 59, ""))
         self.assertTrue(t)
 
-        # But this should yield a value error -- the utcoffset is bogus.
-        t = cls(0, tzinfo=FixedOffset(24*60, ""))
-        self.assertRaises(ValueError, lambda: bool(t))
-
-        # Likewise.
-        t = cls(0, tzinfo=FixedOffset(-24*60, ""))
-        self.assertRaises(ValueError, lambda: bool(t))
-
     def test_replace(self):
         cls = self.theclass
         z100 = FixedOffset(100, "+100")

Misc/NEWS

@@ -23,6 +23,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #13936: Remove the ability of datetime.time instances to be considered
+  false in boolean contexts.
+
 - Issue 18931: selectors module now supports /dev/poll on Solaris.
   Patch by Giampaolo Rodola'.
 

Modules/_datetimemodule.c

@@ -3805,29 +3805,6 @@ time_replace(PyDateTime_Time *self, PyObject *args, PyObject *kw)
     return clone;
 }
 
-static int
-time_bool(PyObject *self)
-{
-    PyObject *offset, *tzinfo;
-    int offsecs = 0;
-
-    if (TIME_GET_SECOND(self) || TIME_GET_MICROSECOND(self)) {
-        /* Since utcoffset is in whole minutes, nothing can
-         * alter the conclusion that this is nonzero.
-         */
-        return 1;
-    }
-    tzinfo = GET_TIME_TZINFO(self);
-    if (tzinfo != Py_None) {
-        offset = call_utcoffset(tzinfo, Py_None);
-        if (offset == NULL)
-            return -1;
-        offsecs = GET_TD_DAYS(offset)*86400 + GET_TD_SECONDS(offset);
-        Py_DECREF(offset);
-    }
-    return (TIME_GET_MINUTE(self)*60 - offsecs + TIME_GET_HOUR(self)*3600) != 0;
-}
-
 /* Pickle support, a simple use of __reduce__. */
 
 /* Let basestate be the non-tzinfo data string.
@@ -3895,19 +3872,6 @@ PyDoc_STR("time([hour[, minute[, second[, microsecond[, tzinfo]]]]]) --> a time
 All arguments are optional. tzinfo may be None, or an instance of\n\
 a tzinfo subclass. The remaining arguments may be ints.\n");
 
-static PyNumberMethods time_as_number = {
-    0,                                          /* nb_add */
-    0,                                          /* nb_subtract */
-    0,                                          /* nb_multiply */
-    0,                                          /* nb_remainder */
-    0,                                          /* nb_divmod */
-    0,                                          /* nb_power */
-    0,                                          /* nb_negative */
-    0,                                          /* nb_positive */
-    0,                                          /* nb_absolute */
-    (inquiry)time_bool,                         /* nb_bool */
-};
-
 static PyTypeObject PyDateTime_TimeType = {
     PyVarObject_HEAD_INIT(NULL, 0)
     "datetime.time",                            /* tp_name */
@@ -3919,7 +3883,7 @@ static PyTypeObject PyDateTime_TimeType = {
     0,                                          /* tp_setattr */
     0,                                          /* tp_reserved */
     (reprfunc)time_repr,                        /* tp_repr */
-    &time_as_number,                            /* tp_as_number */
+    0,                                          /* tp_as_number */
     0,                                          /* tp_as_sequence */
     0,                                          /* tp_as_mapping */
     (hashfunc)time_hash,                        /* tp_hash */