The “does Python have variables?” debate

[Johannes Schneider]

On 08.05.2014 02:35, Ben Finney wrote:
> Marko Rauhamaa <marko at pacujo.net> writes:
[..]
> Python, on the other hand, has this behaviour::
>
>      foo = [1, 2, 3]
>      bar = foo          # ‘bar’ binds to the value ‘[1, 2, 3]’
>      assert foo == bar  # succeeds
>      foo[1] = "spam"    # ‘foo’ *and* ‘bar’ now == [1, "spam", 3]
[..]

IMHO this is the behavior of having a variable pointing to it's value; 
foo to the list and bar to foo.


consider the following:
 >>> def f(l):
...     l[1] = 'foo'
...
 >>> l1 =  [1,2,3]
 >>> f(l1)
 >>> l1
[1, 'foo', 3]

this means, l1 consists of "pointers" to its values.
Otherwise, it's not calling by reference, because

 >>> g(l1)
 >>> l1
[1, 'foo', 3]

does not change l1. Once again, if I pass an object it behaves like 
calling by reference:

 >>> class A:
...     a = 0
...
 >>> a = A()
 >>> a.a
0
 >>> def h(a1):
...     a1.a = 1
...
 >>> h(a)
 >>> a.a
1

bg,
Johannes


-- 
Johannes Schneider
Webentwicklung
johannes.schneider at galileo-press.de
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