diff -r a012d5df2c73 Lib/decimal.py
--- a/Lib/decimal.py	Tue Apr 10 16:27:58 2012 +0200
+++ b/Lib/decimal.py	Tue Apr 10 18:46:19 2012 +0300
@@ -547,7 +547,7 @@
 class Decimal(object):
 """Floating point class for decimal arithmetic."""
 
- __slots__ = ('_exp','_int','_sign', '_is_special')
+ __slots__ = ('_exp','_int','_sign', '_is_special', '_hash')
 # Generally, the value of the Decimal instance is given by
 # (-1)**_sign * _int * 10**_exp
 # Special values are signified by _is_special == True
@@ -983,6 +983,10 @@
 
 def __hash__(self):
 """x.__hash__() <==> hash(x)"""
+ try:
+ return self._hash
+ except AttributeError:
+ pass
 
 # In order to make sure that the hash of a Decimal instance
 # agrees with the hash of a numerically equal integer, float
@@ -992,20 +996,22 @@
 if self.is_snan():
 raise TypeError('Cannot hash a signaling NaN value.')
 elif self.is_nan():
- return _PyHASH_NAN
+ hash_ = _PyHASH_NAN
 else:
 if self._sign:
- return -_PyHASH_INF
+ hash_ = -_PyHASH_INF
 else:
- return _PyHASH_INF
-
- if self._exp>= 0:
- exp_hash = pow(10, self._exp, _PyHASH_MODULUS)
+ hash_ = _PyHASH_INF
 else:
- exp_hash = pow(_PyHASH_10INV, -self._exp, _PyHASH_MODULUS)
- hash_ = int(self._int) * exp_hash % _PyHASH_MODULUS
- ans = hash_ if self>= 0 else -hash_
- return -2 if ans == -1 else ans
+ if self._exp>= 0:
+ exp_hash = pow(10, self._exp, _PyHASH_MODULUS)
+ else:
+ exp_hash = pow(_PyHASH_10INV, -self._exp, _PyHASH_MODULUS)
+ hash_ = int(self._int) * exp_hash % _PyHASH_MODULUS
+ if self < 0: hash_ = -hash_
+ if hash_ == -1: hash_ = -2
+ self._hash = hash_
+ return hash_
 
 def as_tuple(self):
 """Represents the number as a triple tuple.
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