Issue #21470: Do a better job seeding the random number generator

to fully cover its state space.

Lib/random.py

@@ -108,7 +108,9 @@ class Random(_random.Random):
 
         if a is None:
             try:
-                a = long(_hexlify(_urandom(32)), 16)
+                # Seed with enough bytes to span the 19937 bit
+                # state space for the Mersenne Twister
+                a = long(_hexlify(_urandom(2500)), 16)
             except NotImplementedError:
                 import time
                 a = long(time.time() * 256) # use fractional seconds

Misc/NEWS

@@ -52,6 +52,9 @@ Library
 - Issue #21306: Backport hmac.compare_digest from Python 3. This is part of PEP
   466.
 
+- Issue #21470: Do a better job seeding the random number generator by
+  using enough bytes to span the full state space of the Mersenne Twister.
+
 - Issue #21469:  Reduced the risk of false positives in robotparser by
   checking to make sure that robots.txt has been read or does not exist
   prior to returning True in can_fetch().