Issue #2531: Make float-to-decimal comparisons return correct results.
Float to decimal comparison operations now return a result based on
the numeric values of the operands. Decimal.__hash__ has also been
fixed so that Decimal and float values that compare equal have equal
hash value.
diff --git a/Lib/decimal.py b/Lib/decimal.py
index a10bdf2..159669c 100644
--- a/Lib/decimal.py
+++ b/Lib/decimal.py
@@ -855,7 +855,7 @@
# that specified by IEEE 754.
def __eq__(self, other):
- other = _convert_other(other)
+ other = _convert_other(other, allow_float=True)
if other is NotImplemented:
return other
if self.is_nan() or other.is_nan():
@@ -863,7 +863,7 @@
return self._cmp(other) == 0
def __ne__(self, other):
- other = _convert_other(other)
+ other = _convert_other(other, allow_float=True)
if other is NotImplemented:
return other
if self.is_nan() or other.is_nan():
@@ -871,7 +871,7 @@
return self._cmp(other) != 0
def __lt__(self, other, context=None):
- other = _convert_other(other)
+ other = _convert_other(other, allow_float=True)
if other is NotImplemented:
return other
ans = self._compare_check_nans(other, context)
@@ -880,7 +880,7 @@
return self._cmp(other) < 0
def __le__(self, other, context=None):
- other = _convert_other(other)
+ other = _convert_other(other, allow_float=True)
if other is NotImplemented:
return other
ans = self._compare_check_nans(other, context)
@@ -889,7 +889,7 @@
return self._cmp(other) <= 0
def __gt__(self, other, context=None):
- other = _convert_other(other)
+ other = _convert_other(other, allow_float=True)
if other is NotImplemented:
return other
ans = self._compare_check_nans(other, context)
@@ -898,7 +898,7 @@
return self._cmp(other) > 0
def __ge__(self, other, context=None):
- other = _convert_other(other)
+ other = _convert_other(other, allow_float=True)
if other is NotImplemented:
return other
ans = self._compare_check_nans(other, context)
@@ -932,12 +932,18 @@
# The hash of a nonspecial noninteger Decimal must depend only
# on the value of that Decimal, and not on its representation.
# For example: hash(Decimal('100E-1')) == hash(Decimal('10')).
- if self._is_special:
- if self._isnan():
- raise TypeError('Cannot hash a NaN value.')
- return hash(str(self))
- if not self:
- return 0
+ if self._is_special and self._isnan():
+ raise TypeError('Cannot hash a NaN value.')
+
+ # In Python 2.7, we're allowing comparisons (but not
+ # arithmetic operations) between floats and Decimals; so if
+ # a Decimal instance is exactly representable as a float then
+ # its hash should match that of the float. Note that this takes care
+ # of zeros and infinities, as well as small integers.
+ self_as_float = float(self)
+ if Decimal.from_float(self_as_float) == self:
+ return hash(self_as_float)
+
if self._isinteger():
op = _WorkRep(self.to_integral_value())
# to make computation feasible for Decimals with large
@@ -5695,15 +5701,21 @@
##### Helper Functions ####################################################
-def _convert_other(other, raiseit=False):
+def _convert_other(other, raiseit=False, allow_float=False):
"""Convert other to Decimal.
Verifies that it's ok to use in an implicit construction.
+ If allow_float is true, allow conversion from float; this
+ is used in the comparison methods (__eq__ and friends).
+
"""
if isinstance(other, Decimal):
return other
if isinstance(other, (int, long)):
return Decimal(other)
+ if allow_float and isinstance(other, float):
+ return Decimal.from_float(other)
+
if raiseit:
raise TypeError("Unable to convert %s to Decimal" % other)
return NotImplemented