diff options
Diffstat (limited to 'Lib/random.py')
| -rw-r--r-- | Lib/random.py | 104 |
1 files changed, 67 insertions, 37 deletions
diff --git a/Lib/random.py b/Lib/random.py index b9359e4..427b731 100644 --- a/Lib/random.py +++ b/Lib/random.py @@ -66,10 +66,10 @@ used to "move backward in time": >>> g = Random(42) # arbitrary >>> g.random() -0.24855401895528142 +0.25420336316883324 >>> g.jumpahead(6953607871644L - 1) # move *back* one >>> g.random() -0.24855401895528142 +0.25420336316883324 """ # XXX The docstring sucks. @@ -119,26 +119,31 @@ class Random: # different core generator should override the seed(), random(), # getstate(), setstate() and jumpahead() methods. - def __whseed(self, x=0, y=0, z=0): - """Set the Wichmann-Hill seed from (x, y, z). + def seed(self, a=None): + """Initialize internal state from hashable object. - These must be integers in the range [0, 256). + None or no argument seeds from current time. + + If a is not None or an int or long, hash(a) is instead. + + If a is an int or long, a is used directly. Distinct values between + 0 and 27814431486575L inclusive are guaranteed to yield distinct + internal states (this guarantee is specific to the default + Wichmann-Hill generator). """ - if not type(x) == type(y) == type(z) == type(0): - raise TypeError('seeds must be integers') - if not (0 <= x < 256 and 0 <= y < 256 and 0 <= z < 256): - raise ValueError('seeds must be in range(0, 256)') - if 0 == x == y == z: + if a is None: # Initialize from current time import time - t = long(time.time()) * 256 - t = int((t&0xffffff) ^ (t>>24)) - t, x = divmod(t, 256) - t, y = divmod(t, 256) - t, z = divmod(t, 256) - # Zero is a poor seed, so substitute 1 - self._seed = (x or 1, y or 1, z or 1) + a = long(time.time() * 256) + + if type(a) not in (type(3), type(3L)): + a = hash(a) + + a, x = divmod(a, 30268) + a, y = divmod(a, 30306) + a, z = divmod(a, 30322) + self._seed = int(x)+1, int(y)+1, int(z)+1 def random(self): """Get the next random number in the range [0.0, 1.0).""" @@ -171,26 +176,6 @@ class Random: # never return 0.0 (asserted by Tim; proof too long for a comment). return (x/30269.0 + y/30307.0 + z/30323.0) % 1.0 - def seed(self, a=None): - """Seed from hashable object's hash code. - - None or no argument seeds from current time. It is not guaranteed - that objects with distinct hash codes lead to distinct internal - states. - """ - - if a is None: - self.__whseed() - return - a = hash(a) - a, x = divmod(a, 256) - a, y = divmod(a, 256) - a, z = divmod(a, 256) - x = (x + a) % 256 or 1 - y = (y + a) % 256 or 1 - z = (z + a) % 256 or 1 - self.__whseed(x, y, z) - def getstate(self): """Return internal state; can be passed to setstate() later.""" return self.VERSION, self._seed, self.gauss_next @@ -227,6 +212,50 @@ class Random: z = int(z * pow(170, n, 30323)) % 30323 self._seed = x, y, z + def __whseed(self, x=0, y=0, z=0): + """Set the Wichmann-Hill seed from (x, y, z). + + These must be integers in the range [0, 256). + """ + + if not type(x) == type(y) == type(z) == type(0): + raise TypeError('seeds must be integers') + if not (0 <= x < 256 and 0 <= y < 256 and 0 <= z < 256): + raise ValueError('seeds must be in range(0, 256)') + if 0 == x == y == z: + # Initialize from current time + import time + t = long(time.time() * 256) + t = int((t&0xffffff) ^ (t>>24)) + t, x = divmod(t, 256) + t, y = divmod(t, 256) + t, z = divmod(t, 256) + # Zero is a poor seed, so substitute 1 + self._seed = (x or 1, y or 1, z or 1) + + def whseed(self, a=None): + """Seed from hashable object's hash code. + + None or no argument seeds from current time. It is not guaranteed + that objects with distinct hash codes lead to distinct internal + states. + + This is obsolete, provided for compatibility with the seed routine + used prior to Python 2.1. Use the .seed() method instead. + """ + + if a is None: + self.__whseed() + return + a = hash(a) + a, x = divmod(a, 256) + a, y = divmod(a, 256) + a, z = divmod(a, 256) + x = (x + a) % 256 or 1 + y = (y + a) % 256 or 1 + z = (z + a) % 256 or 1 + self.__whseed(x, y, z) + ## ---- Methods below this point do not need to be overridden when ## ---- subclassing for the purpose of using a different core generator. @@ -623,6 +652,7 @@ weibullvariate = _inst.weibullvariate getstate = _inst.getstate setstate = _inst.setstate jumpahead = _inst.jumpahead +whseed = _inst.whseed if __name__ == '__main__': _test() |