How to Teach Python "Variables"

[Diez B. Roggisch]

Aurélien Campéas schrieb:
> none a écrit :
>>     Hello,
>>
>>     IIRC, I once saw an explanation how Python doesn't have 
>> "variables" in the sense that, say, C does, and instead has bindings 
>> from names to objects. Does anyone have a link?
>>
>>     Thanks,
>>
>>     Ami
> 
> That's something I've often heard and I don't get it. Somehow I don't 
> understand how C variables are not like python bindings (the differences 
> being that C variables are statically typed and completely disappear at 
> run-time; are these differences important enough to warrant such a shift 
> in terminology ? (yes there are some other differences, but then the 
> question is asked in a context of pedagogy, where the audience is 
> introduced to the basics))
> 
> I mean : aren't C variables also bindings from names to objects ? Or what ?

There are cruicial differences. In C, you have names pointing to 
physical memory locations - fixed locations, that is.

Thus you can do e.g.

some_struct a, b;

a = b = some_struct_value;

a.bar = 10;
b.bar = 20;

Now a.bar will be different from b.bar

This is totally different from python semantics, where


a = b = some_object

a.bar = 10
b.bar = 20

will result in both times the same object being manipulated.

So python variables are more equivalent to pointers in C.

Diez