Issue 2748: fix __ceil__, __floor__ and __round__ magic methods in
Decimal, and add tests.
diff --git a/Lib/decimal.py b/Lib/decimal.py
index f008b5a..a61025a 100644
--- a/Lib/decimal.py
+++ b/Lib/decimal.py
@@ -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.