Convert symbolic expression to array in python

Question

I'm trying to convert a symbolic expression to an array in python.

For example, I have this symbolic expression:

import sympy as sp
import numpy as np
A,B = sp.symbols("A B")
G = 3*A**2*B - 2*A*B + A**2

What I want is to convert this to an array looking as follows:

[3*A**2*B,-2*A*B,A**2]

I know how to do this in Matlab, but I need to do it in Python as well.

What I've tried:
I've converted the symbolic expression to a polynomial, which allowed me to collect the coefficients.

C = G.as_poly().coeffs()

This gets me halfway there:

C = [3,-2,1]

But I want to have at least a similar list for all the variables.

Does anyone have an idea?

Shaido · Accepted Answer · 2020-04-14 10:09:19Z

2

You can use as_ordered_terms to get an ordered list of all the terms:

G.as_ordered_terms()

gives

[3*A**2*B, A**2, -2*A*B]

Alternatively, you can use args to get all the top-level arguments of the object.

G.args

This will give a tuple:

(A**2, -2*A*B, 3*A**2*B)

answered Apr 14, 2020 at 10:09

Shaido

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