Thank you for your answer and sorry for the typo mistake. Your solution works well with the example given but doesn't work as I would like with exponents (x^2, ...).
What I would like to get is Sage returning expressions with coefficients sorted by the value of the exponents, like when using multivariate polynomial rings. Here is an example : ***************************** var('x y z A B') f = (1+B*(x+y))^((B-1)/(2*B)) * exp(z/2) / (1+(x-y)/A) f = taylor(f,(x,0),(y,0),(z,0),2) #this definition of a polynomial ring is useless R.<A,B> = QQ[] R.<x,y,z> = PolynomialRing(QQ[A,B],order='deglex') print f ***************************** I want to sort the terms of a polynomial obtained with a Taylor expansion. I cannot declare a polynomial ring to have the terms automatically sorted because the initial expression is not a polynomial. I tried to ask Sage to switch to a polynomial ring after applying the Taylor expansion, but it doesn't change anyting. What I would like to obtain is the following answer (I copied/pasted the solution of the Taylor expansion and I worked in a polynomial ring) : ***************************** R.<A,B> = QQ[] R.<x,y,z> = PolynomialRing(QQ[A,B],order='deglex') f = 1/2*(((B - 1)*A - 2)*x + ((B - 1)*A + 2)*y + A*z)/A + 1/8*(A^2*z^2 - ((B^2 - 1)*A^2 - 4*(B - 1)*A - 8)*y^2 - ((B^2 - 1)*A^2 + 4*(B - 1)*A - 8)*x^2 + 2*((B - 1)*A^2 + 2*A)*y*z - 2*(((B^2 - 1)*A^2 + 8)*y - ((B - 1)*A^2 - 2*A)*z)*x)/A^2 + 1 print f ***************************** Is there a solution to my problem ? Thanks -- You received this message because you are subscribed to the Google Groups "sage-support" group. To post to this group, send email to sage-support@googlegroups.com. To unsubscribe from this group, send email to sage-support+unsubscr...@googlegroups.com. Visit this group at http://groups.google.com/group/sage-support?hl=en.