learning python ...

[hw]

On 5/25/21 12:37 AM, Greg Ewing wrote:
> On 25/05/21 9:27 am, Cameron Simpson wrote:
>> On 24May2021 16:17, hw <hw at adminart.net> wrote:
>  >
>>> Or it doesn't forget
>>> about the old one and the old one becomes inaccessible (unless you
>>> have a reference to it, if there is such a thing in python).  How do
>>> you call that?
>>
>> You're conflating values
>> (objects, such as an int or a string) with variables (which _are_
>> references in Python,
> 
> I think hw might have meant the C++ notion of a reference to
> a *variable*. There is no equivalent of that in Python.

yes, or a reference in perl

> Python does have references to *objects*. All objects live on
> the heap and are kept alive as long as there is at least one
> reference to them.
> 
> If you rebind a name, and it held the last reference to an
> object, there is no way to get that object back.

Are all names references?  When I pass a name as a parameter to a 
function, does the object the name is referring to, when altered by the 
function, still appear altered after the function has returned?  I 
wouldn't expect that ...

> On the other hand, if you shadow a name, the original name
> still exists, and there is usually some way to get at it,
> e.g.
> 
>  >>> int = 42
>  >>> int
> 42
>  >>> __builtins__.int
> <class 'int'>
>  >>>
> 

You mean built-in objects never go away, even when they are no longer 
referenced?