no side effects

[Michele Simionato]

holger krekel <pyth at devel.trillke.net> wrote in message news:<mailman.1042039926.12943.python-list at python.org>...
> "Martin v. L?wis" wrote:
> > holger krekel wrote:
> > > 'i' might not be local but usually it is.  When answering 
> > > newcomer questions i try to refrain from talking in language
> > > lawyer details (as much as possible).  I only tried to explain the 
> > > for-loop from the viewpoint of names bound to objects.  I didn't 
> > > want to compare iteration protocols between python and C++ just 
> > > to explain that. 
> > 
> > I'm uncertain though whether an actually incorrect explanation helps the 
> > newcomer.
> 
> Of course, it shouldn't be incorrect.  I don't think i actually was. 
> 
> > Namespaces are totally irrelevant for this feature of the for loop.
> 
> Depends on your background.  *If* somebody e.g. thinks that 
> 
>     for i in range(3):
>         print i
>         i = 3
> 
> is somewhat equivalent to C's
> 
>     int i;
>     for (i=0 ; i<3 ; i++) {
>         printf("%d\n", i);
>         i = 3;
>     }
> 
> then IMHO my explanation serves well and talking about underlying 
> iterator protocols wouldn't help too much.  
> 
> Why is the way the python for-loop gets to the next *value* 
> more important than understanding that python works with 
> name-object bindings everywhere?  And what is so wrong 
> about this (*)? 
> 
> slightly irritated,
> 
>     holger
> 
> 
> (*) see http://www.python.org/dev/doc/devel/ref/naming.html
>     for further details.

If I may defend Holger, I had in mind exactly the C example he wrote.
The namespace argument maybe of not relevance here (yes, it is better
to think of i as a variable local to the loop), nevertheless it has
be useful to me to be reminded that Python interprets "variables"
in a quite difference sense from C. I tend to forget it sometimes.
I think I am not the only one who can be fooled by this example.

Cheers,

                                 Michele

P.S. I forgot to post the output of the script, which is 1 2 3.
And yes, the indentation is correct.