Restore Poly from dict

[Paul Royik]

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...

[Aaron Meurer]

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

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[Paul Royik]

Thank you.