Stefan,
Thanks for the explanation on the first item. My second item was typed in
error ( and somehow the corrected post has not showed up yet). So, let me
elaborate on the second issue.
I have a t1 = Tr(A*B*C), and I set A,B,C = symbols('A B C',
commutative=False).
Now, I have a method where I let the user do a cyclic permute on t1's
arguments using t1.permute(1). This permute method returns t2 = Tr(C*A*B).
So far everything works fine. Until, this point I have not overridden the
_hashable_content() method.
Now, I need to override my _hashable_contents() method so that I always
return args 'A,B,C' ( in that order), so that t1==t2 evaluates to True
(cycle property of trace).
But, once I implemented the _hashable_contents() method, id(t2) is always
equal to id(t1). Which means I am not able to return Tr(C*A*B) when I call
the permute method.
Makes sense?
Thanks
Guru
On Friday, June 22, 2012 3:22:46 PM UTC-5, Stefan Krastanov wrote:
>
> On 22 June 2012 22:13, Guru Devanla <[email protected]> wrote:
> > Hello All,
> >
> > Can someone explain why 2 objects in the following statements give me
> the
> > same id() value?
> >
> >
> >>>> A, B = symbols('A B', commutative=False)
> >>>> x = A*B
> >>>> print id(x)
> > 169853492
> >>>> y = A*B
> >>>> print id(y)
> > 169853492
>
> Because these are the same object A*B. x and y are just labels
> pointing to an instance.
>
> >
> > I run into this problem while trying to implement some operation on
> Trace
> > module.
> >
> > Say, I have Tr(A*B*C) . Now, the user wants to create another instance
> of
> > Tr(C*A*B). But, both objects are getting the same id, meaning I am not
> > able to create 2 different objects one which prints at Tr(A*B*C) and
> another
> > which prints as Tr(C*A*B). Note, that I have not yet overridden
> > _hashable_contents to compare the args ( using the cyclic property of
> > trace).
> >
> Stupid question: Did you correctly set commutable=False for A,B and C.
> Does Tr somehow override them?
>
> > Am I missing something basic? Or is there a way to override this
> > behavior, if necessary
> >
> > Thanks
> > Guru
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
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