[Python-3000-checkins] r62938 - in python/branches/py3k: Lib/decimal.py Lib/test/test_decimal.py Misc/NEWS
mark.dickinson
python-3000-checkins at python.org
Fri May 9 15:42:34 CEST 2008
Author: mark.dickinson
Date: Fri May 9 15:42:33 2008
New Revision: 62938
Log:
Issue 2748: fix __ceil__, __floor__ and __round__ magic methods in
Decimal, and add tests.
Modified:
python/branches/py3k/Lib/decimal.py
python/branches/py3k/Lib/test/test_decimal.py
python/branches/py3k/Misc/NEWS
Modified: python/branches/py3k/Lib/decimal.py
==============================================================================
--- python/branches/py3k/Lib/decimal.py (original)
+++ python/branches/py3k/Lib/decimal.py Fri May 9 15:42:33 2008
@@ -1645,9 +1645,6 @@
else:
return -1
- def __round__(self):
- return self._round_down(0)
-
def _round_up(self, prec):
"""Rounds away from 0."""
return -self._round_down(prec)
@@ -1683,9 +1680,6 @@
else:
return -self._round_down(prec)
- def __ceil__(self):
- return self._round_ceiling(0)
-
def _round_floor(self, prec):
"""Rounds down (not towards 0 if negative)"""
if not self._sign:
@@ -1693,9 +1687,6 @@
else:
return -self._round_down(prec)
- def __floor__(self):
- return self._round_floor(0)
-
def _round_05up(self, prec):
"""Round down unless digit prec-1 is 0 or 5."""
if prec and self._int[prec-1] not in '05':
@@ -1703,6 +1694,102 @@
else:
return -self._round_down(prec)
+ def __round__(self, n=None):
+ """Round self to the nearest integer, or to a given precision.
+
+ If only one argument is supplied, round a finite Decimal
+ instance self to the nearest integer. If self is infinite or
+ a NaN then a Python exception is raised. If self is finite
+ and lies exactly halfway between two integers then it is
+ rounded to the integer with even last digit.
+
+ >>> round(Decimal('123.456'))
+ 123
+ >>> round(Decimal('-456.789'))
+ -457
+ >>> round(Decimal('-3.0'))
+ -3
+ >>> round(Decimal('2.5'))
+ 2
+ >>> round(Decimal('3.5'))
+ 4
+ >>> round(Decimal('Inf'))
+ Traceback (most recent call last):
+ ...
+ ...
+ ...
+ OverflowError: cannot round an infinity
+ >>> round(Decimal('NaN'))
+ Traceback (most recent call last):
+ ...
+ ...
+ ...
+ ValueError: cannot round a NaN
+
+ If a second argument n is supplied, self is rounded to n
+ decimal places using the rounding mode for the current
+ context.
+
+ For an integer n, round(self, -n) is exactly equivalent to
+ self.quantize(Decimal('1En')).
+
+ >>> round(Decimal('123.456'), 0)
+ Decimal('123')
+ >>> round(Decimal('123.456'), 2)
+ Decimal('123.46')
+ >>> round(Decimal('123.456'), -2)
+ Decimal('1E+2')
+ >>> round(Decimal('-Infinity'), 37)
+ Decimal('NaN')
+ >>> round(Decimal('sNaN123'), 0)
+ Decimal('NaN123')
+
+ """
+ if n is not None:
+ # two-argument form: use the equivalent quantize call
+ if not isinstance(n, int):
+ raise TypeError('Second argument to round should be integral')
+ exp = _dec_from_triple(0, '1', -n)
+ return self.quantize(exp)
+
+ # one-argument form
+ if self._is_special:
+ if self.is_nan():
+ raise ValueError("cannot round a NaN")
+ else:
+ raise OverflowError("cannot round an infinity")
+ return int(self._rescale(0, ROUND_HALF_EVEN))
+
+ def __floor__(self):
+ """Return the floor of self, as an integer.
+
+ For a finite Decimal instance self, return the greatest
+ integer n such that n <= self. If self is infinite or a NaN
+ then a Python exception is raised.
+
+ """
+ if self._is_special:
+ if self.is_nan():
+ raise ValueError("cannot round a NaN")
+ else:
+ raise OverflowError("cannot round an infinity")
+ return int(self._rescale(0, ROUND_FLOOR))
+
+ def __ceil__(self):
+ """Return the ceiling of self, as an integer.
+
+ For a finite Decimal instance self, return the least integer n
+ such that n >= self. If self is infinite or a NaN then a
+ Python exception is raised.
+
+ """
+ if self._is_special:
+ if self.is_nan():
+ raise ValueError("cannot round a NaN")
+ else:
+ raise OverflowError("cannot round an infinity")
+ return int(self._rescale(0, ROUND_CEILING))
+
def fma(self, other, third, context=None):
"""Fused multiply-add.
Modified: python/branches/py3k/Lib/test/test_decimal.py
==============================================================================
--- python/branches/py3k/Lib/test/test_decimal.py (original)
+++ python/branches/py3k/Lib/test/test_decimal.py Fri May 9 15:42:33 2008
@@ -1150,6 +1150,94 @@
self.assertEqual(float(d1), 66)
self.assertEqual(float(d2), 15.32)
+ #floor
+ test_pairs = [
+ ('123.00', 123),
+ ('3.2', 3),
+ ('3.54', 3),
+ ('3.899', 3),
+ ('-2.3', -3),
+ ('-11.0', -11),
+ ('0.0', 0),
+ ('-0E3', 0),
+ ]
+ for d, i in test_pairs:
+ self.assertEqual(math.floor(Decimal(d)), i)
+ self.assertRaises(ValueError, math.floor, Decimal('-NaN'))
+ self.assertRaises(ValueError, math.floor, Decimal('sNaN'))
+ self.assertRaises(ValueError, math.floor, Decimal('NaN123'))
+ self.assertRaises(OverflowError, math.floor, Decimal('Inf'))
+ self.assertRaises(OverflowError, math.floor, Decimal('-Inf'))
+
+ #ceiling
+ test_pairs = [
+ ('123.00', 123),
+ ('3.2', 4),
+ ('3.54', 4),
+ ('3.899', 4),
+ ('-2.3', -2),
+ ('-11.0', -11),
+ ('0.0', 0),
+ ('-0E3', 0),
+ ]
+ for d, i in test_pairs:
+ self.assertEqual(math.ceil(Decimal(d)), i)
+ self.assertRaises(ValueError, math.ceil, Decimal('-NaN'))
+ self.assertRaises(ValueError, math.ceil, Decimal('sNaN'))
+ self.assertRaises(ValueError, math.ceil, Decimal('NaN123'))
+ self.assertRaises(OverflowError, math.ceil, Decimal('Inf'))
+ self.assertRaises(OverflowError, math.ceil, Decimal('-Inf'))
+
+ #round, single argument
+ test_pairs = [
+ ('123.00', 123),
+ ('3.2', 3),
+ ('3.54', 4),
+ ('3.899', 4),
+ ('-2.3', -2),
+ ('-11.0', -11),
+ ('0.0', 0),
+ ('-0E3', 0),
+ ('-3.5', -4),
+ ('-2.5', -2),
+ ('-1.5', -2),
+ ('-0.5', 0),
+ ('0.5', 0),
+ ('1.5', 2),
+ ('2.5', 2),
+ ('3.5', 4),
+ ]
+ for d, i in test_pairs:
+ self.assertEqual(round(Decimal(d)), i)
+ self.assertRaises(ValueError, round, Decimal('-NaN'))
+ self.assertRaises(ValueError, round, Decimal('sNaN'))
+ self.assertRaises(ValueError, round, Decimal('NaN123'))
+ self.assertRaises(OverflowError, round, Decimal('Inf'))
+ self.assertRaises(OverflowError, round, Decimal('-Inf'))
+
+ #round, two arguments; this is essentially equivalent
+ #to quantize, which is already extensively tested
+ test_triples = [
+ ('123.456', -4, '0E+4'),
+ ('123.456', -3, '0E+3'),
+ ('123.456', -2, '1E+2'),
+ ('123.456', -1, '1.2E+2'),
+ ('123.456', 0, '123'),
+ ('123.456', 1, '123.5'),
+ ('123.456', 2, '123.46'),
+ ('123.456', 3, '123.456'),
+ ('123.456', 4, '123.4560'),
+ ('123.455', 2, '123.46'),
+ ('123.445', 2, '123.44'),
+ ('Inf', 4, 'NaN'),
+ ('-Inf', -23, 'NaN'),
+ ('sNaN314', 3, 'NaN314'),
+ ]
+ for d, n, r in test_triples:
+ self.assertEqual(str(round(Decimal(d), n)), r)
+
+
+
def test_eval_round_trip(self):
#with zero
Modified: python/branches/py3k/Misc/NEWS
==============================================================================
--- python/branches/py3k/Misc/NEWS (original)
+++ python/branches/py3k/Misc/NEWS Fri May 9 15:42:33 2008
@@ -18,6 +18,10 @@
Library
-------
+- The Decimal module gained the magic methods __round__, __ceil__,
+ __floor__ and __trunc__, to give support for round, math.ceil,
+ math.floor and math.trunc.
+
- The user module has been removed.
- The mutex module has been removed.
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