From 24d3deefcf2f78b12fc29ed4c9a3811d46c534bb Mon Sep 17 00:00:00 2001 From: Alexander Belopolsky Date: Sat, 28 Feb 2015 10:41:57 -0500 Subject: Fixes #23521: Corrected pure python implementation of timedelta division. * Eliminated OverflowError from timedelta * float for some floats; * Corrected rounding in timedlta true division. --- Lib/datetime.py | 26 +++++++++++++++++++++++--- 1 file changed, 23 insertions(+), 3 deletions(-) (limited to 'Lib/datetime.py') diff --git a/Lib/datetime.py b/Lib/datetime.py index 1789714034..4c442f2139 100644 --- a/Lib/datetime.py +++ b/Lib/datetime.py @@ -280,6 +280,25 @@ def _cmperror(x, y): raise TypeError("can't compare '%s' to '%s'" % ( type(x).__name__, type(y).__name__)) +def _divide_and_round(a, b): + """divide a by b and round result to the nearest integer + + When the ratio is exactly half-way between two integers, + the even integer is returned. + """ + # Based on the reference implementation for divmod_near + # in Objects/longobject.c. + q, r = divmod(a, b) + # round up if either r / b > 0.5, or r / b == 0.5 and q is odd. + # The expression r / b > 0.5 is equivalent to 2 * r > b if b is + # positive, 2 * r < b if b negative. + r *= 2 + greater_than_half = r > b if b > 0 else r < b + if greater_than_half or r == b and q % 2 == 1: + q += 1 + + return q + class timedelta: """Represent the difference between two datetime objects. @@ -506,8 +525,9 @@ class timedelta: self._seconds * other, self._microseconds * other) if isinstance(other, float): + usec = self._to_microseconds() a, b = other.as_integer_ratio() - return self * a / b + return timedelta(0, 0, _divide_and_round(usec * a, b)) return NotImplemented __rmul__ = __mul__ @@ -532,10 +552,10 @@ class timedelta: if isinstance(other, timedelta): return usec / other._to_microseconds() if isinstance(other, int): - return timedelta(0, 0, usec / other) + return timedelta(0, 0, _divide_and_round(usec, other)) if isinstance(other, float): a, b = other.as_integer_ratio() - return timedelta(0, 0, b * usec / a) + return timedelta(0, 0, _divide_and_round(b * usec, a)) def __mod__(self, other): if isinstance(other, timedelta): -- cgit v1.2.1