From: Raymond Hettinger <python@rcn.com>
Date: Sat, 9 Aug 2003 18:30:57 +0000 (+0000)
Subject: SF bug #778964:  bad seed in python 2.3 random
X-Git-Tag: v2.4a1~1767
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=3081d59f920229b26293c7a3ee3f1a9da0da53e9;p=thirdparty%2FPython%2Fcpython.git

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.
---

diff --git a/Lib/random.py b/Lib/random.py
index 76dc41699a50..7932ac71e9d0 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 ea2243d1de91..c9103e8f87b7 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 1de08e7249f6..93c7fb8b8d59 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.