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Cutting a deck of cards

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  Cutting a deck of cards RVic <rvince99@gmail.com> - 2013-05-26 10:52 -0700
    Re: Cutting a deck of cards MRAB <python@mrabarnett.plus.com> - 2013-05-26 19:04 +0100
    Re: Cutting a deck of cards Kamlesh Mutha <mkamlesh@gmail.com> - 2013-05-26 23:35 +0530
    RE: Cutting a deck of cards Carlos Nepomuceno <carlosnepomuceno@outlook.com> - 2013-05-26 21:16 +0300
      Re: Cutting a deck of cards Marc Christiansen <usenetmail@solar-empire.de> - 2013-05-26 21:36 +0200
        RE: Cutting a deck of cards Carlos Nepomuceno <carlosnepomuceno@outlook.com> - 2013-05-26 22:54 +0300
          Re: Cutting a deck of cards Marc Christiansen <usenetmail@solar-empire.de> - 2013-05-26 22:13 +0200
        Re: Cutting a deck of cards Terry Jan Reedy <tjreedy@udel.edu> - 2013-05-26 17:03 -0400
    Re: Cutting a deck of cards RVic <rvince99@gmail.com> - 2013-05-26 11:17 -0700
    Re: Cutting a deck of cards Roy Smith <roy@panix.com> - 2013-05-26 14:21 -0400
    Re: Cutting a deck of cards Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-05-26 23:17 +0100
    RE: Cutting a deck of cards Carlos Nepomuceno <carlosnepomuceno@outlook.com> - 2013-05-27 01:30 +0300
    Re: Cutting a deck of cards Chris Angelico <rosuav@gmail.com> - 2013-05-27 08:42 +1000
    RE: Cutting a deck of cards Carlos Nepomuceno <carlosnepomuceno@outlook.com> - 2013-05-27 01:51 +0300
    Re: Cutting a deck of cards Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-05-26 23:56 +0100
    Re: Cutting a deck of cards Lee Crocker <leedanielcrocker@gmail.com> - 2013-05-31 04:56 -0700
      Re: Cutting a deck of cards Modulok <modulok@gmail.com> - 2013-05-31 12:54 -0600
      Re: Cutting a deck of cards Joshua Landau <joshua.landau.ws@gmail.com> - 2013-06-01 18:16 +0100
        Re: Cutting a deck of cards Lee Crocker <leedanielcrocker@gmail.com> - 2013-06-01 22:57 -0700
    Re: Cutting a deck of cards Giorgos Tzampanakis <giorgos.tzampanakis@gmail.com> - 2013-06-01 14:58 +0000

#46088 — Cutting a deck of cards

Suppose I have a deck of cards, and I shuffle them

import random
cards = []
decks = 6
cards = list(range(13 * 4 * decks))
random.shuffle(cards)

So now I have an array of cards. I would like to cut these cards at some random point (between 1 and 13 * 4 * decks - 1, moving the lower half of that to the top half of the cards array.

For some reason, I can't see how this can be done (I know that it must be a simple line or two in Python, but I am really stuck here). Anyone have any direction they can give me on this? Thanks, RVic, python newbie

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#46089

On 26/05/2013 18:52, RVic wrote:
> Suppose I have a deck of cards, and I shuffle them
>
> import random
> cards = []
> decks = 6
> cards = list(range(13 * 4 * decks))
> random.shuffle(cards)
>
> So now I have an array of cards. I would like to cut these cards at some random point (between 1 and 13 * 4 * decks - 1, moving the lower half of that to the top half of the cards array.
>
> For some reason, I can't see how this can be done (I know that it must be a simple line or two in Python, but I am really stuck here). Anyone have any direction they can give me on this? Thanks, RVic, python newbie
>
The list from its start up to, but excluding, index 'i' is cards[ : i],
and the list from index 'i' to its end is cards[i : ].

Now concatenate them those slices.

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#46090

[Multipart message — attachments visible in raw view] — view raw

I guess, you will have to use list slicing mechanism to achieve the desired
result.

Hope this helps,

Cheers,
Kamlesh





On Sun, May 26, 2013 at 11:22 PM, RVic <rvince99@gmail.com> wrote:

> Suppose I have a deck of cards, and I shuffle them
>
> import random
> cards = []
> decks = 6
> cards = list(range(13 * 4 * decks))
> random.shuffle(cards)
>
> So now I have an array of cards. I would like to cut these cards at some
> random point (between 1 and 13 * 4 * decks - 1, moving the lower half of
> that to the top half of the cards array.
>
> For some reason, I can't see how this can be done (I know that it must be
> a simple line or two in Python, but I am really stuck here). Anyone have
> any direction they can give me on this? Thanks, RVic, python newbie
>
> --
> http://mail.python.org/mailman/listinfo/python-list
>



-- 
Faith waiting in the heart of a seed promises a miracle of life which it
can not prove!
-Ravindranath Tagore

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#46094

----------------------------------------
> Date: Sun, 26 May 2013 10:52:14 -0700
> Subject: Cutting a deck of cards
> From: rvince99@gmail.com
> To: python-list@python.org
>
> Suppose I have a deck of cards, and I shuffle them
>
> import random
> cards = []
> decks = 6
> cards = list(range(13 * 4 * decks))
> random.shuffle(cards)
>
> So now I have an array of cards. I would like to cut these cards at some random point (between 1 and 13 * 4 * decks - 1, moving the lower half of that to the top half of the cards array.
>
> For some reason, I can't see how this can be done (I know that it must be a simple line or two in Python, but I am really stuck here). Anyone have any direction they can give me on this? Thanks, RVic, python newbie
>
> --
> http://mail.python.org/mailman/listinfo/python-list


list(range(13 * 4 * decks)) == range(13 * 4 * decks)

;) 		 	   		  

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#46105

Carlos Nepomuceno <carlosnepomuceno@outlook.com> wrote:
> ----------------------------------------
>> Date: Sun, 26 May 2013 10:52:14 -0700
>> Subject: Cutting a deck of cards
>> From: rvince99@gmail.com
>> To: python-list@python.org
>>
>> Suppose I have a deck of cards, and I shuffle them
>>
>> import random
>> cards = []
>> decks = 6
>> cards = list(range(13 * 4 * decks))
>> random.shuffle(cards)
>>
>> So now I have an array of cards. I would like to cut these cards at
>> some random point (between 1 and 13 * 4 * decks - 1, moving the lower
>> half of that to the top half of the cards array.
>>
>> For some reason, I can't see how this can be done (I know that it
>> must be a simple line or two in Python, but I am really stuck here).
>> Anyone have any direction they can give me on this? Thanks, RVic,
>> python newbie
>>
>> --
>> http://mail.python.org/mailman/listinfo/python-list
> 
> 
> list(range(13 * 4 * decks)) == range(13 * 4 * decks)
> 
> ;)                                        

Not in Python3.x
>>> decks = 6
>>> list(range(13 * 4 * decks)) == range(13 * 4 * decks)
False

Adiaŭ
Marc

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#46109

----------------------------------------
> From: usenetmail@solar-empire.de
[...]
> Not in Python3.x
>>>> decks = 6
>>>> list(range(13 * 4 * decks)) == range(13 * 4 * decks)
> False
>
> Adiaŭ
> Marc


What does "list(range(13 * 4 * decks))" returns in Python 3? 		 	   		  

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#46112

Carlos Nepomuceno <carlosnepomuceno@outlook.com> wrote:
> ----------------------------------------
>> From: usenetmail@solar-empire.de
> [...]
>> Not in Python3.x
>>>>> decks = 6
>>>>> list(range(13 * 4 * decks)) == range(13 * 4 * decks)
>> False
> 
> What does "list(range(13 * 4 * decks))" returns in Python 3?                                      

A list of course. But Py3 range is very similar to Py2 xrange, it
returns a range object.

Adiaŭ
Marc

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#46121

On 5/26/2013 3:54 PM, Carlos Nepomuceno wrote:
> ----------------------------------------
>> From: usenetmail@solar-empire.de
> [...]
>> Not in Python3.x
>>>>> decks = 6
>>>>> list(range(13 * 4 * decks)) == range(13 * 4 * decks)
>> False
>>
>> Adiaŭ
>> Marc
>
>
> What does "list(range(13 * 4 * decks))" returns in Python 3? 	

A list, obviously. What you should ask is what range returns in Python 
3, and you should install python 3 and try it, and list its attributes.
	 	   		

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#46095

Ah, brilliant -- yes, this is so much more elegant in Python:

#now cut the cards
x = random.randrange(2,range(13 * 4 * decks))
cards = cards[x:]+cards[:x]

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#46097

In article <4d02f46f-8264-41bf-a254-d1c20469626e@googlegroups.com>,
 RVic <rvince99@gmail.com> wrote:

> Suppose I have a deck of cards, and I shuffle them
> 
> import random
> cards = []
> decks = 6
> cards = list(range(13 * 4 * decks))
> random.shuffle(cards)
> 
> So now I have an array of cards. I would like to cut these cards at some 
> random point (between 1 and 13 * 4 * decks - 1, moving the lower half of that 
> to the top half of the cards array.
> 
> For some reason, I can't see how this can be done (I know that it must be a 
> simple line or two in Python, but I am really stuck here). Anyone have any 
> direction they can give me on this? Thanks, RVic, python newbie

import random
i = random.randrange(len(cards))
cut1 = cards[:i]
cut2 = cards[i:]

I haven't thought too much about the boundary conditions, but that's the 
general idea.

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#46131

On 26/05/2013 19:16, Carlos Nepomuceno wrote:
> ----------------------------------------
>> Date: Sun, 26 May 2013 10:52:14 -0700
>> Subject: Cutting a deck of cards
>> From: rvince99@gmail.com
>> To: python-list@python.org
>>
>> Suppose I have a deck of cards, and I shuffle them
>>
>> import random
>> cards = []
>> decks = 6
>> cards = list(range(13 * 4 * decks))
>> random.shuffle(cards)
>>
>> So now I have an array of cards. I would like to cut these cards at some random point (between 1 and 13 * 4 * decks - 1, moving the lower half of that to the top half of the cards array.
>>
>> For some reason, I can't see how this can be done (I know that it must be a simple line or two in Python, but I am really stuck here). Anyone have any direction they can give me on this? Thanks, RVic, python newbie
>>
>> --
>> http://mail.python.org/mailman/listinfo/python-list
>
>
> list(range(13 * 4 * decks)) == range(13 * 4 * decks)
>
> ;) 		 	   		
>

Wrong if you're using Python 3 :(

-- 
If you're using GoogleCrap™ please read this 
http://wiki.python.org/moin/GoogleGroupsPython.

Mark Lawrence

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#46136

----------------------------------------
> To: python-list@python.org
> From: breamoreboy@yahoo.co.uk
[...]
> Wrong if you're using Python 3 :(
>
> --
> If you're using GoogleCrap™ please read this
> http://wiki.python.org/moin/GoogleGroupsPython.
>
> Mark Lawrence


Thanks guys! I've been delaying my dive into Python 3 (because I don't need it for now) but I'd like to run some code just to learn how different it is from Python 2 and even other Python flavors.

So, I'd like to know if it's possible to have multiple Python installations on the same machine (Windows 7 in my particular case) without messing one with each other. What care must I take not to mess up with them?

I've just found this[1] awesome service, but ridiculously it's PHP powered!!! lol Come on!!!

Why there aren't more Python powered websites available? What's the catch?


[1] http://www.compileonline.com/execute_python3_online.php 		 	   		  

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#46140

On Mon, May 27, 2013 at 8:30 AM, Carlos Nepomuceno
<carlosnepomuceno@outlook.com> wrote:
> Thanks guys! I've been delaying my dive into Python 3 (because I don't need it for now) but I'd like to run some code just to learn how different it is from Python 2 and even other Python flavors.
>
> So, I'd like to know if it's possible to have multiple Python installations on the same machine (Windows 7 in my particular case) without messing one with each other. What care must I take not to mess up with them?

Easy. Just grab the standard installer and hit it. You'll get two
separate directories (or more; I have \Python26, \Python27, \Python32,
\Python33 on this box), and you can run whichever you want. The one
thing to take care of is .py associations; I haven't actually done it
(on here, all I actually do is IDLE, pretty much), but as of 3.3, you
should be able to use a Unix-style shebang to indicate which Python
you want to invoke.

ChrisA

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#46141

----------------------------------------
> Date: Mon, 27 May 2013 08:42:56 +1000
> Subject: Re: Cutting a deck of cards
> From: rosuav@gmail.com
[...]
> Easy. Just grab the standard installer and hit it. You'll get two
> separate directories (or more; I have \Python26, \Python27, \Python32,
> \Python33 on this box), and you can run whichever you want. The one
> thing to take care of is .py associations; I haven't actually done it
> (on here, all I actually do is IDLE, pretty much), but as of 3.3, you
> should be able to use a Unix-style shebang to indicate which Python
> you want to invoke.
>
> ChrisA

I'm not even using shebangs in Windows because I thought it wouldn't make any difference. I'm used to run scripts like "python filename.py" from the command line. No problem!

So, Python 3.3 will honor if I insert "#!C:\Python27\python.exe"? if I install it after Python 2.7? Cool!!! 		 	   		  

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#46143

On 26/05/2013 23:42, Chris Angelico wrote:
> On Mon, May 27, 2013 at 8:30 AM, Carlos Nepomuceno
> <carlosnepomuceno@outlook.com> wrote:
>> Thanks guys! I've been delaying my dive into Python 3 (because I don't need it for now) but I'd like to run some code just to learn how different it is from Python 2 and even other Python flavors.
>>
>> So, I'd like to know if it's possible to have multiple Python installations on the same machine (Windows 7 in my particular case) without messing one with each other. What care must I take not to mess up with them?
>
> Easy. Just grab the standard installer and hit it. You'll get two
> separate directories (or more; I have \Python26, \Python27, \Python32,
> \Python33 on this box), and you can run whichever you want. The one
> thing to take care of is .py associations; I haven't actually done it
> (on here, all I actually do is IDLE, pretty much), but as of 3.3, you
> should be able to use a Unix-style shebang to indicate which Python
> you want to invoke.
>
> ChrisA
>

See this 
http://docs.python.org/3/whatsnew/3.3.html#pep-397-python-launcher-for-windows

-- 
If you're using GoogleCrap™ please read this 
http://wiki.python.org/moin/GoogleGroupsPython.

Mark Lawrence

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#46599

Why on Earth would you want to? "Cutting" a deck makes no sense in software. Randomize the deck properly (Google "Fisher-Yates") and start dealing. Cutting the deck will not make it any more random, and in fact will probably make it worse depending on how you choose the cutpoint.

The purpose of "cutting" cards is to make it more difficult for human dealers to stack a deck. Simulating it in software makes no more sense than simulating the cigars you smoke while playing.

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#46625

[Multipart message — attachments visible in raw view] — view raw

> Why on Earth would you want to? "Cutting" a deck makes no sense in
> software. Randomize the deck properly (Google "Fisher-Yates") and start
> dealing. Cutting the deck will not make it any more random, and in fact
> will probably make it worse depending on how you choose the cutpoint.
>
> The purpose of "cutting" cards is to make it more difficult for human
> dealers to stack a deck. Simulating it in software makes no more sense than
> simulating the cigars you smoke while playing.
>
>
Perhaps the OP wanted to study the efficiency and affect of a real-world
shuffling algorithm :-p Maybe he was designing a probabilistic magic trick
and
needed to evaluate how a cut would modify the outcome of a particular stack.
Maybe it was a school assignment. Who knows?

(But yeah if the purpose was for pure randomization then there's no real
point.)

There could be a lot of legitimate reasons though.
-Modulok-

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#46668

On 31 May 2013 12:56, Lee Crocker <leedanielcrocker@gmail.com> wrote:
> Why on Earth would you want to? "Cutting" a deck makes no sense in software. Randomize the deck properly (Google "Fisher-Yates") and start dealing. Cutting the deck will not make it any more random,

True

> and in fact will probably make it worse depending on how you choose the cutpoint.

I'm pretty sure it won't. Otherwise you'd be lowering entropy by doing
a random thing to a random thing.

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#46680

>> and in fact will probably make it worse depending on how you choose
>> the cutpoint.
 
> I'm pretty sure it won't. Otherwise you'd be lowering entropy by doing
> a random thing to a random thing.

Doing a random thing to a random thing usually *does* lower entropy when
the "random" things are actually deterministic algorithms that may have unexpected correlations. That's why you don't write your own PRNG unless
you have a very good understanding of the math.

If you are shuffling the deck with, say, numbers from random.org (which uses atmospheric noise), then cutting the deck afterward will have precisely 0 effect, since the (51 * 52!) possible outcomes include 51 copies of each of the 52! orderings, and so the odds of each end up the same. But if you're choosing the cutpoint by getting a value from the same PRNG you used to shuffle, there might very well be a correlation that makes some arrangements more likely
than others.

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#46664

On 2013-05-26, RVic wrote:

> Suppose I have a deck of cards, and I shuffle them
>
> import random
> cards = []
> decks = 6
> cards = list(range(13 * 4 * decks))
> random.shuffle(cards)
>
> So now I have an array of cards. I would like to cut these cards at some
> random point (between 1 and 13 * 4 * decks - 1, moving the lower half of
> that to the top half of the cards array.
>
> For some reason, I can't see how this can be done (I know that it must
> be a simple line or two in Python, but I am really stuck here). Anyone
> have any direction they can give me on this? Thanks, RVic, python newbie
>

The slice notation should be your friend here:

random.shuffle(cards)
cut_point = random.choice(xrange(len(cards)))
cards = cards[cut_point :] + cards[: cut_point]

-- 
Real (i.e. statistical) tennis and snooker player rankings and ratings:
http://www.statsfair.com/ 

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