Roulette wheel

[mattia]

Il Thu, 05 Mar 2009 12:54:39 +0100, Peter Otten ha scritto:

> mattia wrote:
> 
>> Il Thu, 05 Mar 2009 10:46:58 +0100, Peter Otten ha scritto:
>> 
>>> mattia wrote:
>>> 
>>>>> Note how get_roulette_wheel() is now completeley independent of the
>>>>> concrete problem you are using it for.
>>>> 
>>>> Ok, but also a lot more memory consuming ;-)
>>> 
>>> I don't think so. Python references objects; therefore the list
>>> 
>>> [tiny_little_thing]*N
>>> 
>>> does not consume more memory than
> 
> Oops, should have been less.
> 
> 
>>> [big_fat_beast]*N
>>> 
>>> Or did you have something else in mind?
>>> 
>>> Peter
>> 
>> Ok, understood. So if I have e.g. [[200 elements]]*N, then I'll have N
>> pointers to the same location of my seq, right?
> 
> Right. You can verify this with
> 
>>>> v = [0]
>>>> items = [v]*5
>>>> v[0] = 42
>>>> items
> [[42], [42], [42], [42], [42]]
> 
> which often surprises newbies.
> 
> Peter

Great explanation, thanks.