Values and objects

[Rustom Mody]

On Saturday, May 10, 2014 6:31:49 AM UTC+5:30, Steven D'Aprano wrote:
> On Sat, 10 May 2014 01:34:58 +0300, Marko Rauhamaa wrote:

> 
> > and you can't pass references to them.
> 
> 
> That at least you have got right.
> 

And that's Marko's main point

> 
> 
> > Right, Python's variables aren't like variables in C. Rather, Python's
> > variables are like CPU registers. They cannot hold typed or structured
> > objects 
> 
> 
> Surely you cannot mean that? It is *trivially simple* to disprove that 
> statement:
> 
> 
> py> x = [1, 2, 3]  # A structured object
> py> type(x)  # that has a type
> <class 'list'>

You missed the 'hold'

For me, Marko's comment that variables in python are not first-class
whereas in C they are is for me the most important distinction Ive seen
(in a long time of seeing these discussions).

In C a pointer is a 'pre-variable' in this sense:
int i, *p;
p = &i

after this
i and *p are completely interchangeable

However p can also refer to -- (contain?hold?) depends on which side of this debate you are -- an element of an array or struct
p = &some_array[some_index]
p = &some_struct.some_field

And all the way to anonymity with
p = malloc(sizeof(*p))

This is what makes p a kind of meta-variable:
- it can 'contain' other variables
- it can contain variale-ish things like array elements
- it can contain new variables on the fly via malloc

These possibilities dont exist in python