Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.python > #19894

Re: difference between random module in python 2.6 and 3.2?

Show all headers | View raw

On 2/6/2012 12:56 AM, Steven D'Aprano wrote:
> On Mon, 06 Feb 2012 00:07:04 -0500, Terry Reedy wrote:
>
>> On 2/5/2012 11:01 PM, Steven D'Aprano wrote:
>>
>>> Reading the docs, I would expect that when using an int as seed, you
>>> should get identical results.
>>
>> That is similar to expecting hash to be consistent from version to
>> version.
>
> No. hash is not intended to be consistent across versions, or even across

Oh, but it was. Changing it will break tests, including some in the 
Python test suite.

...
> This, plus Raymond Hettinger's comments on the bug report, make me think
> that the change in behaviour of randrange and choice is not deliberate

As I said, it was a necessary consequence of a bug fix.

> and should be treated as a bug. Raymond made a strong case arguing for
> repeatability, and then approved a bug fix that broke repeatability. I
> doubt that was deliberate.

It was deliberate that randrange was changed to an even distribution 
from a slightly uneven distribute. That implies a change in the pattern. 
That was known and the main subject of discussion. As Antoine said, 
making functions exactly repeatable across versions means not fixing 
bugs or otherwise improving them. This statement is not limited to the 
random module.

You have persuaded me that the doc should be more explicit that while 
the basic random.random sequence will be kept repeatable with seed set 
(except perhaps after a changeover of several releases), the convenience 
transformations can be changed if improvements are needed or thought 
sufficiently desirable.

-- 
Terry Jan Reedy

Back to comp.lang.python | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

difference between random module in python 2.6 and 3.2? Matej Cepl <mcepl@redhat.com> - 2012-02-06 02:27 +0100
  Re: difference between random module in python 2.6 and 3.2? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-02-06 04:01 +0000
    Re: difference between random module in python 2.6 and 3.2? Terry Reedy <tjreedy@udel.edu> - 2012-02-06 00:07 -0500
      Re: difference between random module in python 2.6 and 3.2? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-02-06 05:56 +0000
        Re: difference between random module in python 2.6 and 3.2? Terry Reedy <tjreedy@udel.edu> - 2012-02-06 02:27 -0500
          Re: difference between random module in python 2.6 and 3.2? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-02-06 08:05 +0000
            Re: difference between random module in python 2.6 and 3.2? Matej Cepl <mcepl@redhat.com> - 2012-02-06 09:45 +0100
              Re: difference between random module in python 2.6 and 3.2? Matej Cepl <mcepl@redhat.com> - 2012-02-06 09:57 +0100
                Re: difference between random module in python 2.6 and 3.2? Tim Chase <python.list@tim.thechases.com> - 2012-02-06 13:26 -0600
                Re: difference between random module in python 2.6 and 3.2? Matej Cepl <mcepl@redhat.com> - 2012-02-06 23:06 +0100
                Re: difference between random module in python 2.6 and 3.2? Serhiy Storchaka <storchaka@gmail.com> - 2012-02-07 12:05 +0200
              Re: difference between random module in python 2.6 and 3.2? Ulrich Eckhardt <ulrich.eckhardt@dominolaser.com> - 2012-02-07 16:11 +0100
            Re: difference between random module in python 2.6 and 3.2? Mel Wilson <mwilson@the-wire.com> - 2012-02-06 10:20 -0500

csiph-web