[Python-checkins] CVS: python/dist/src/Lib random.py,1.21,1.22

[Tim Peters]

Update of /cvsroot/python/python/dist/src/Lib
In directory usw-pr-cvs1:/tmp/cvs-serv14254/python/dist/src/Lib

Modified Files:
	random.py 
Log Message:
Change random.seed() so that it can get at the full range of possible
internal states.  Put the old .seed() (which could only get at about
the square root of the # of possibilities) under the new name .whseed(),
for bit-level compatibility with older versions.  This occurred to me
while reviewing effbot's book (he found himself stumbling over .seed()
more than once there ...).


Index: random.py
===================================================================
RCS file: /cvsroot/python/python/dist/src/Lib/random.py,v
retrieving revision 1.21
retrieving revision 1.22
diff -C2 -r1.21 -r1.22
*** random.py	2001/01/26 22:56:56	1.21
--- random.py	2001/02/01 04:59:18	1.22
***************
*** 67,74 ****
  >>> g = Random(42)  # arbitrary
  >>> g.random()
! 0.24855401895528142
  >>> g.jumpahead(6953607871644L - 1) # move *back* one
  >>> g.random()
! 0.24855401895528142
  """
  # XXX The docstring sucks.
--- 67,74 ----
  >>> g = Random(42)  # arbitrary
  >>> g.random()
! 0.25420336316883324
  >>> g.jumpahead(6953607871644L - 1) # move *back* one
  >>> g.random()
! 0.25420336316883324
  """
  # XXX The docstring sucks.
***************
*** 120,143 ****
      # getstate(), setstate() and jumpahead() methods.
  
!     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 random(self):
--- 120,148 ----
      # getstate(), setstate() and jumpahead() methods.
  
!     def seed(self, a=None):
!         """Initialize internal state from hashable object.
  
!         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 a is None:
              # Initialize from current time
              import time
!             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):
***************
*** 172,195 ****
          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."""
--- 177,180 ----
***************
*** 228,231 ****
--- 213,260 ----
          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.
***************
*** 624,627 ****
--- 653,657 ----
  setstate = _inst.setstate
  jumpahead = _inst.jumpahead
+ whseed = _inst.whseed
  
  if __name__ == '__main__':