Automatic debugging of copy by reference errors?

[Gabriel Genellina]

On 9 dic, 02:22, "Niels L Ellegaard" <niels.ellega... at gmail.com> wrote:

> Is there a module that allows me to find errors that occur due to copy
> by reference?

What do you mean by "copy by reference"?

> I am looking for something like the following:
>
> >>> import mydebug
> >>> mydebug.checkcopybyreference = True
> >>> a=2
> >>> b=[a]
> >>> a=4
> Traceback (most recent call last):
>   File "<stdin>", line 1, in ?
> CopyByReferenceError: Variable b refers to variable a, so please do not
> change variable a.

(I won't be pedantic to say that Python has no "variables"). What's
wrong with that code? You are *not* changing "variable a", you are
binding the integer 4 to the name "a". That name used previously to be
bound to another integer, 2 - what's wrong with it? Anyway it has no
effect on the list referred by the name "b", still holds b==[2]
What do you want? Forbid the re-use of names? So once you say a=2, you
can't modify it? That could be done, yes, a "write-once-read-many"
namespace. But I don't see the usefullness.

> Does such a module exist?
No
> Would it be possible to code such a module?
I don't know what do you want to do exactly, but I feel it's not
useful.
> Would it be possible to add the functionality to array-copying in
> numpy?
No idea.
> What would be the extra cost in terms of memory and CPU power?
No idea yet.
> I realize that this module would disable some useful features of the
> language.
Not only "some useful features", most programs would not even work!
> On the other hand it could be helpful for new python users.
I think you got in trouble with something and you're trying to avoid it
again - but perhaps this is not the right way. Could you provide some
example?

-- 
Gabriel Genellina