Beginner Question

Alex Martelli aleax at aleax.it
Fri Mar 28 12:08:01 CET 2003


Kevin Reeder wrote:

> On Thu, 27 Mar 2003 20:45:04 -0800, Lee Harr wrote:
> 
>> Well... it is not just the last line, but I think the best way would be:
>> 
>> import random
>> def shuffle(self):
>>     random.shuffle(self.cards)
> 
> This one failed to work with the exception: Attribute error: shuffle.
> Probably something I'm not seeing.

Weird.  Can you please try to reproduce the error "in the small" and
just copy and paste it to a post rather than summarizing it?  For me
it works just fine, e.g.:


>>> import random
>>> def shuffle(self):
...   random.shuffle(self.cards)
...
>>> class X:
...   cards = list('pacilokeruny')
...
>>> shuffle(X)
>>> X.cards
['u', 'k', 'r', 'y', 'a', 'e', 'c', 'o', 'l', 'p', 'i', 'n']
>>>

What happens when YOU try this exact code?  If this works and your
script doesn't, what's the essential difference that breaks your
script?


>> def shuffle(self):
>>     import random
>>     nCards = len(self.cards)
>>     for i in range(nCards):
>>         j = random.randrange(i, nCards)
>>         self.cards.insert(i, self.cards.pop(j))
> 
> This solution worked great. Is insert a list method?

Yes, it is.  But in your shoes I'd invest more effort in trying
to make random.shuffle work -- it's going to be faster (with Tim
Peters having programmed it, that's almost guaranteed;-) AND
you're going to feel more secure in its correctness (ditto) -- this
one does seem OK, but inspection might miss some subtle issue...
using solid modules from the standard library is just safer!-)


Alex





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