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Multivariate polynomial coefficients including zeros

Dears,

I would like to get the coefficients of a multivariate polynomial including the zero coefficients (in their correct positions). I have found a similar answer as regards a polynomial f of two variables x,y

P.<x,y> = PolynomialRing(ZZ, 2, order='lex') 
f=3*x^2*y^2+x*y+3

Then using the following code:

coeffs = []
for i in range(f.degree(x), -1, -1):
  for j in range(f.degree(y), -1, -1):
      coeffs.append(f.coefficient({x:i, y:j}))

The result is as expected: [3, ,0 , 0, 1, 0, 0, 0, 0, 3]

Now, I would like to extend this solution for a multivariate polynomial of n variables [xo,x1,...xn-1] The polynomial is defined with the following code: (Note: q=next_prime(10000))

A1 = [(', '.join('x%i'%i for i in [0.. n-1]))]; ### construct a suitable multivariate ring
V = var(A1[0])
 x=vector(list(V))
P1=PolynomialRing(GF(q),V)

How can I do that? Any help will be much appreciated.

Regards, Natassa