It looks like Poly.from_dict will do it:
In [6]: p = Poly(6*x**4*y**5 + 3*x*y**2,y,x)
In [7]: p.as_dict()
Out[7]: {(2, 1): 3, (5, 4): 6}
In [8]: p.from_dict(p.as_dict(), y, x)
Out[8]: Poly(6*y**5*x**4 + 3*y**2*x, y, x, domain='ZZ')
The order of the generators is the same as the order in the Poly. I
don't remember if there is a better method on Poly for reordering
generators, but in the above example Poly(p, x, y) will reorder them.
Aaron Meurer
On Fri, Mar 27, 2015 at 2:50 PM, Paul Royik <distantjob...@gmail.com> wrote:
> Suppose I have following polynomial:
> poly= Poly(6*x**4*y**5 + 3*x*y**2,y,x)
>
> It's dictionary is
> poly.as_dict() # {(5, 4): 6, (2, 1): 3}
>
>
> How can I restore poly from dict?
> How do I know that (5, 4) - > (y, x) ?
> poly.free_symbols is set, so it is unordered.
>
> Is there any way to fetch that from Poly?
>
> One way I think is following:
>
> variables = [x,y]
> poly= Poly(6*x**4*y**5 + 3*x*y**2,variables)
>
> #(5, 4) - > variables
>
>
> And next question: how are coeffcients are ordered? Can I change order?
> order keyword throws exception...
>
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