How to extract the free term of a polynomial with symbolic coefficients?

Specific Domains Modelling & Simulations
1

Let’s say, I use Symbolics.jl to define a polynomial in λ with symbolic coefficients.

using Symbolics
@variables λ p q

f = λ^3 + p*λ + q

How do I get the free term of the polynomial with respect to λ?
I can use Symbolics.coeff(f, λ^3) and Symbolics.coeff(f, λ) to extract the coefficients of the first two terms, but Symbolics.coeff(f, λ^0) just returns 0, although I want to get q.

2

Here is what I got:

julia> sum(filter(t->Symbolics.degree(t,λ)==0,terms(f)))
q

Caveat: Not a Symbolics user.

3

A bit late, but you could simply use

julia> substitute(f, λ => 0)
q

Side note: If you want to do more involved stuff with polynomials, maybe have a look at Oscar.jl.