Terminology: “reference” versus “pointer”

Random832 random832 at fastmail.com
Sat Sep 12 08:15:40 CEST 2015


Mark Lawrence <breamoreboy at yahoo.co.uk> writes:

> No it isn't.  When you make a copy of an object you will end up with
> two names that refer to the same object.

No, when you *make a copy of* an object, you get two objects.

>>> x = [1, 2, 3]
>>> y = copy.copy(x)
>>> x is y
False

What you make a copy of when you do y = x is not the object.

> If y was a copy of x, then when x is blown away how can y still know
> about the list that x originally referred to?

Because what is in x, and therefore what is copied when you assign y =
x, *is* the knowledge of how to find the list. Not the list itself. The
object is also not what is deleted when you delete it.

And deleting the original does not delete a copy and I don't even
understand how you can possibly think it could.



More information about the Python-list mailing list