Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > comp.lang.python > #54913
| Date | 2013-09-27 17:40 -0400 |
|---|---|
| From | Ned Batchelder <ned@nedbatchelder.com> |
| Subject | Re: card dealer |
| References | <0617088e-5aa3-4c5d-b660-22040ee858a1@googlegroups.com> <l23q0r$u27$1@ger.gmane.org> <mailman.380.1380283737.18130.python-list@python.org> <l24am7$j2k$2@dont-email.me> |
| Newsgroups | comp.lang.python |
| Message-ID | <mailman.394.1380318056.18130.python-list@python.org> (permalink) |
On 9/27/13 12:10 PM, Denis McMahon wrote: > On Fri, 27 Sep 2013 12:08:33 +0000, Dave Angel wrote: > >> i recall >> writing a shuffle function in C decades ago, which took an array of (52) >> unique items and put them in random order. > Whenever I tried to write shuffles I came up against a fairly fundamental > limit: > > 52! > prng states > > Granted prngs seem to be better on the importing entropy from elsewhere > front these days. > Python's PRNG holds plenty of state to handle card shuffling. Python's random number generator has a period of 2**19337-1, so it has that many states. That is much larger than 52!, about 10**5933 times larger. (Unless I've botched the math...) The other variable is how many states the initial seed can have. If os.urandom is available, then it seeds with 16 bytes of OS-supplied randomness. But 52! is about 2**226, so the 128 bits of seed isn't enough to make all shuffles possible. You could seed a Random yourself with more bits if you really wanted to. --Ned.
Back to comp.lang.python | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
card dealer markotaht@gmail.com - 2013-09-27 03:24 -0700
Re: card dealer Dave Angel <davea@davea.name> - 2013-09-27 11:26 +0000
Re: card dealer MRAB <python@mrabarnett.plus.com> - 2013-09-27 12:27 +0100
Re: card dealer Alister <alister.ware@ntlworld.com> - 2013-09-27 11:41 +0000
Re: card dealer Dave Angel <davea@davea.name> - 2013-09-27 12:08 +0000
Re: card dealer Denis McMahon <denismfmcmahon@gmail.com> - 2013-09-27 16:10 +0000
Re: card dealer Dave Angel <davea@davea.name> - 2013-09-27 21:00 +0000
Re: card dealer Ned Batchelder <ned@nedbatchelder.com> - 2013-09-27 17:40 -0400
Re: card dealer Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-09-28 06:01 +0000
Re: card dealer Ned Batchelder <ned@nedbatchelder.com> - 2013-09-28 06:31 -0400
Re: card dealer Dave Angel <davea@davea.name> - 2013-09-28 12:56 +0000
Re: card dealer Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-09-28 16:49 +0200
Re: card dealer Tim Roberts <timr@probo.com> - 2013-09-28 17:04 -0700
csiph-web