[Tutor] Having trouble with a component of the random module

[OmerT]

I'm unfamiliar with the random.sample function, yet I can't help but wonder:
Do you ever got the same card twice?
Is that intentional ?



On Thu, Aug 28, 2008 at 6:29 PM, Alan Gilfoy <agilfoy at frontiernet.net> wrote:
> Quoting W W <srilyk at gmail.com>:
>
>
>>> The number of items I want from a list is smaller than the population
>>> (number of items) in the list, so it should work.
>>>
>>> In this specific case, I'm asking for one item from a five-item list.
>>
>> Are you sure?
>>
>> change this:
>>  for card in random.sample(SpecialA, SA):
>>
>> to this:
>>
>> print "Special: ", SpecialA, "\nSA: ", SA
>> for card in random.sample(SpecialA, SA):
>>
>> then give us the output. I'll bet that your SA value is never reset to 1.
>>
> There is a part of my front-end code that declares the SA variable as equal
> to 1 for the card set in question, and feeds that into the processing
> function.
> Changing the block of code, as you suggest, still gets me a traceback:
>
> Special:  []
> SA:  1
>
> Traceback (most recent call last):
>  File "C:\Documents and Settings\Alan\My
> Documents\_Alan_Programming\trunk\BoosterPackMaker\BoosterPackMaker.py",
> line 104, in <module>
>    SixList_PackChooser(C_list, UC_list, R_list, BL_list, SpecialA_list,
> SpecialB_list, C, UC, R, BL, SA, SB)
>  File "C:\Documents and Settings\Alan\My
> Documents\_Alan_Programming\trunk\BoosterPackMaker\PackGenerator.py", line
> 367, in SixList_PackChooser
>    for card in random.sample(SpecialA, SA):
>  File "C:\Python25\lib\random.py", line 303, in sample
>    raise ValueError, "sample larger than population"
> ValueError: sample larger than population
>
> So, I'm asking my program to pick 1 item from a 0-item list. How there are
> zero items in the list, I don't know. That must be the problem.
>
>>
>> You've obviously researched enough to know this:
>>>>>
>>>>> mylist = [1, 2, 3, 4, 5]
>>>>> from random import sample
>>>>> sample(mylist, 3)
>>
>> [2, 1, 4]
>>>>>
>>>>> sample(mylist, 10)
>>
>> Traceback (most recent call last):
>>  File "<stdin>", line 1, in <module>
>>  File "/usr/lib/python2.5/random.py", line 303, in sample
>>    raise ValueError, "sample larger than population"
>> ValueError: sample larger than population
>>
> Okay, asking for 3 items from a 5-item list works, and asking for 10 items
> from a 5-item list doesn't work. It should be trying to pick 1 item from the
> 5-item SpecialA list, but somehow the SpecialA list has zero items in it.
>>
>> So give the print statement before your for loop a try and see what you
>> come
>> up with.
>
> Okay, I cut'n'pasted it before the traceback message.
>>
>> HTH,
>> Wayne
>
> Thank you.
> -----------------------------------------------
> SixList_PackChooser(C_list, UC_list, R_list, BL_list, SpecialA_list,
> SpecialB_list, C, UC, R, BL, SA, SB)
>
> ^ The error occurs in this function.
> The program picks C number of items from C_list and displays them just fine.
> The program picks UC number of items from UC_list and displays them just
> fine.
> The program picks R number of items from R_list and displays them just fine.
> The program picks BL number of items from BL_list and displays them just
> fine.
>
> Looking at my user-interface/front-end, it looks like the function's being
> fed proper values.
>
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