Mark Dickinson
added the comment:
And here's the updated decimal.__hash__ patch that goes with the
long.__hash__ patch.
_____________________________________
Tracker <[EMAIL PROTECTED]>
<http://bugs.python.org/issue1772851>
_____________________________________
Index: Lib/decimal.py
===================================================================
--- Lib/decimal.py (revision 58158)
+++ Lib/decimal.py (working copy)
@@ -770,10 +770,17 @@
if self._isnan():
raise TypeError('Cannot hash a NaN value.')
return hash(str(self))
- i = int(self)
- if self == Decimal(i):
- return hash(i)
- assert self.__nonzero__() # '-0' handled by integer case
+ if not self:
+ return 0
+ if self._isinteger():
+ op = _WorkRep(self.to_integral_value())
+ # to make computation feasible for Decimals with large
+ # exponent, we use the fact that hash(n) == hash(m) for
+ # any two nonzero integers n and m such that (i) n and m
+ # have the same sign, and (ii) n is congruent to m modulo
+ # 2**64-1. So we can replace hash((-1)**s*c*10**e) with
+ # hash((-1)**s*c*pow(10, e, 2**64-1).
+ return hash((-1)**op.sign*op.int*pow(10, op.exp, 2**64-1))
return hash(str(self.normalize()))
def as_tuple(self):
Index: Lib/test/test_decimal.py
===================================================================
--- Lib/test/test_decimal.py (revision 58158)
+++ Lib/test/test_decimal.py (working copy)
@@ -910,6 +910,38 @@
def test_hash_method(self):
#just that it's hashable
hash(Decimal(23))
+
+ test_values = [Decimal(sign*(2**m + n))
+ for m in [0, 14, 15, 16, 17, 30, 31,
+ 32, 33, 62, 63, 64, 65, 66]
+ for n in range(-10, 10)
+ for sign in [-1, 1]]
+ test_values.extend([
+ Decimal("-0"), # zeros
+ Decimal("0.00"),
+ Decimal("-0.000"),
+ Decimal("0E10"),
+ Decimal("-0E12"),
+ Decimal("10.0"), # negative exponent
+ Decimal("-23.00000"),
+ Decimal("1230E100"), # positive exponent
+ Decimal("-4.5678E50"),
+ # a value for which hash(n) != hash(n % (2**64-1))
+ # in Python pre-2.6
+ Decimal(2**64 + 2**32 - 1),
+ # selection of values which fail with the old (before
+ # version 2.6) long.__hash__
+ Decimal("1.634E100"),
+ Decimal("90.697E100"),
+ Decimal("188.83E100"),
+ Decimal("1652.9E100"),
+ Decimal("56531E100"),
+ ])
+
+ # check that hash(d) == hash(int(d)) for integral values
+ for value in test_values:
+ self.assertEqual(hash(value), hash(int(value)))
+
#the same hash that to an int
self.assertEqual(hash(Decimal(23)), hash(23))
self.assertRaises(TypeError, hash, Decimal('NaN'))
_______________________________________________
Python-bugs-list mailing list
Unsubscribe:
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
