From 3081d59f920229b26293c7a3ee3f1a9da0da53e9 Mon Sep 17 00:00:00 2001 From: Raymond Hettinger Date: Sat, 9 Aug 2003 18:30:57 +0000 Subject: SF bug #778964: bad seed in python 2.3 random The default seed is time.time(). Multiplied by 256 before truncating so that fractional seconds are used. This way, two successive calls to random.seed() are much more likely to produce different sequences. --- Lib/random.py | 3 +++ Lib/test/test_random.py | 2 +- Misc/NEWS | 4 ++++ 3 files changed, 8 insertions(+), 1 deletion(-) diff --git a/Lib/random.py b/Lib/random.py index 76dc416..7932ac7 100644 --- a/Lib/random.py +++ b/Lib/random.py @@ -94,6 +94,9 @@ class Random(_random.Random): If a is not None or an int or long, hash(a) is used instead. """ + if a is None: + import time + a = long(time.time() * 256) # use fractional seconds super(Random, self).seed(a) self.gauss_next = None diff --git a/Lib/test/test_random.py b/Lib/test/test_random.py index ea2243d..c9103e8 100644 --- a/Lib/test/test_random.py +++ b/Lib/test/test_random.py @@ -20,7 +20,7 @@ class TestBasicOps(unittest.TestCase): def test_autoseed(self): self.gen.seed() state1 = self.gen.getstate() - time.sleep(1.1) + time.sleep(0.1) self.gen.seed() # diffent seeds at different times state2 = self.gen.getstate() self.assertNotEqual(state1, state2) diff --git a/Misc/NEWS b/Misc/NEWS index 1de08e7..93c7fb8 100644 --- a/Misc/NEWS +++ b/Misc/NEWS @@ -25,6 +25,10 @@ Extension modules Library ------- +- random.seed() with no arguments or None uses time.time() as a default + seed. Modified to match Py2.2 behavior and use fractional seconds so + that successive runs are more likely to produce different sequences. + - itertools.izip() with no arguments now returns an empty iterator instead of raising a TypeError exception. -- cgit v0.12