Is 'everything' a refrence or isn't it?

Claudio Grondi claudio.grondi at freenet.de
Thu Jan 5 10:57:51 CET 2006


Stuart D. Gathman wrote:
> On Wed, 04 Jan 2006 10:54:17 -0800, KraftDiner wrote:
> 
> 
>>I was under the assumption that everything in python was a refrence...
>>
>>so if I code this:
>>lst = [1,2,3]
>>for i in lst:
>>   if i==2:
>>      i = 4
>>print lst
>>
>>I though the contents of lst would be modified.. (After reading that
>>'everything' is a refrence.)
>>...
>>Have I misunderstood something?
> 
> 
> It might help to do a translation to equivalent C:
> 
> int _i1 = 1;
> int _i2 = 2;
> int _i3 = 3;
> int _i4 = 4;
> int* lst[NLST] = { &_i1,&_i2,&_i3 };
> int _idx;	/* internal iterator */
> for (_idx = 0; _idx < NLST; ++_idx) {
>   int *i = lst[_idx];
>   if (*i == *_i2)
     ^-- I have trouble with this line. Is it as is should be? I suppose 
it is not.

Claudio
>     i = &_i4;
> }
> for (_idx = 0; _idx < NLST; ++_idx)
>   printf("%d\n",*lst[_idx]);
> 



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