1

Use expression.find with SR.wild in python scripts

asked 2021-10-27 16:21:11 +0100

Spirit
25 ●1 ●5

I want to detect polynomials of the form x^n + m in a python script.

Found this helpful piece of code that works perfectly in sage's jupyter notebook:

x = var('x')
w0 = SR.wild(0)
w1 = SR.wild(1)
(x**2-2).find(x**w0+w1)

However, when I throw this into a .py file and run it I get the error *** TypeError: unsupported operand parent(s) for ^: 'Symbolic Ring' and 'Symbolic Ring'

Minimal Failing Example:

from sage.all import *
import sage
from sage.calculus.var import var

from sage.symbolic.ring import SymbolicRing
SR = SymbolicRing()
polynomial = SR('x^2-2')

x = var('x')
w0 = SR.wild(0)
w1 = SR.wild(1)
polynomial.find(x**w0+w1)

What am I missing?

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1 Answer

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answered 2021-10-27 19:26:37 +0100

10919 ●4 ●80 ●218 https://www.rburing.nl/

updated 2021-10-27 19:30:58 +0100

The problem is that the x in polynomial is not the x = var('x'):

>>> x is polynomial.variables()[0]
False

It is better to be explicit:

>>> x = SR.var('x')
>>> polynomial = x**2 - 2
>>> polynomial.find(x**w0+w1)
[x^2 - 2]
>>> polynomial.match(x**w0+w1)
{$1: -2, $0: 2}

Or, if you would like to use the preparser:

>>> x = SR.var('x')
>>> polynomial = sage_eval('x^2 - 2', locals={'x' : x})

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Asked: 2021-10-27 16:21:11 +0100

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Last updated: Oct 27 '21

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