# cpython-withatomic / Lib / whrandom.py

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99``` ```# WICHMANN-HILL RANDOM NUMBER GENERATOR # # Wichmann, B. A. & Hill, I. D. (1982) # Algorithm AS 183: # An efficient and portable pseudo-random number generator # Applied Statistics 31 (1982) 188-190 # # see also: # Correction to Algorithm AS 183 # Applied Statistics 33 (1984) 123 # # McLeod, A. I. (1985) # A remark on Algorithm AS 183 # Applied Statistics 34 (1985),198-200 # # # USE: # whrandom.random() yields double precision random numbers # uniformly distributed between 0 and 1. # # whrandom.seed(x, y, z) must be called before whrandom.random() # to seed the generator # # There is also an interface to create multiple independent # random generators, and to choose from other ranges. # Translated by Guido van Rossum from C source provided by # Adrian Baddeley. class whrandom: # # Initialize an instance. # Without arguments, initialize from current time. # With arguments (x, y, z), initialize from them. # def __init__(self, x = 0, y = 0, z = 0): self.seed(x, y, z) # # Set the seed from (x, y, z). # These must be integers in the range [0, 256). # def seed(self, x = 0, y = 0, z = 0): 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) self._seed = (x, y, z) # # Get the next random number in the range [0.0, 1.0). # def random(self): x, y, z = self._seed # x1, x2 = divmod(x, 177) y1, y2 = divmod(y, 176) z1, z2 = divmod(z, 178) # x = (171 * x2 - 2 * x1) % 30269 y = (172 * y2 - 35 * y1) % 30307 z = (170 * z2 - 63 * z1) % 30323 # self._seed = x, y, z # return (x/30269.0 + y/30307.0 + z/30323.0) % 1.0 # # Get a random number in the range [a, b). # def uniform(self, a, b): return a + (b-a) * self.random() # # Get a random integer in the range [a, b] including both end points. # def randint(self, a, b): return a + int(self.random() * (b+1-a)) # # Choose a random element from a non-empty sequence. # def choice(self, seq): return seq[int(self.random() * len(seq))] # Initialize from the current time # _inst = whrandom() seed = _inst.seed random = _inst.random uniform = _inst.uniform randint = _inst.randint choice = _inst.choice ```