Hello,

I wrote a very simple script using sympy, and things were working fine, except for one problem. So I have:

from sympy import *

x, y = symbols('x','y',real=True)
alpha,beta,gamma=symbols('alpha','beta','gamma',real=True)
alpha_p,beta_p,gamma_p=symbols('alpha_p','beta_p','gamma_p',real=True)

L = symbols('L',real=True)



and then I look at solutions to some equations, like:

solution=solve([beta*y - alpha*(1+y/L) ,
                -beta_p*x + alpha_p ], [x, y])

print solution


which prints (correctly):

{x: alpha_p/beta_p, y: L*alpha/(-alpha + L*beta)}

now, if I do:

solution=solve([beta*y - alpha*(1+y/L) - gamma*x*(1+y/L),
                -beta_p*x + alpha_p - gamma_p*y], [x, y])

print solution

I get a very long solution, which isn't a problem, but it isn't a dictionary: I can't tell what is the solution for x and for y. What I get is:

[(-(alpha*beta_p*abs(gamma)*abs(gamma_p) + alpha_p*gamma*abs(gamma) *abs(gamma_p) - L*beta*beta_p*abs(gamma)*abs(gamma_p) - L*gamma*gamma_p*abs(gamma)*abs(gamma_p) - gamma*gamma_p* (2*alpha*alpha_p*beta_p*gamma - 2*L*alpha_p*beta*beta_p*gamma + 2*L*alpha*beta_p*gamma*gamma_p + alpha**2*beta_p**2 + alpha_p**2*gamma**2 + L**2*beta**2*beta_p**2 + L**2*gamma**2*gamma_p**2 - 2*L*alpha*beta*beta_p**2 + 2*L*alpha_p*gamma_p*gamma**2 + 2*beta*beta_p*gamma*gamma_p*L**2)** (1/2))/(2*beta_p*gamma*abs(gamma)*abs(gamma_p)) + alpha_p/beta_p, (alpha*beta_p*abs(gamma)*abs(gamma_p) + alpha_p*gamma*abs(gamma)*abs (gamma_p) - L*beta*beta_p*abs(gamma)*abs(gamma_p) - L*gamma*gamma_p*abs(gamma)*abs(gamma_p) - gamma*gamma_p* (2*alpha*alpha_p*beta_p*gamma - 2*L*alpha_p*beta*beta_p*gamma + 2*L*alpha*beta_p*gamma*gamma_p + alpha**2*beta_p**2 + alpha_p**2*gamma**2 + L**2*beta**2*beta_p**2 + L**2*gamma**2*gamma_p**2 - 2*L*alpha*beta*beta_p**2 + 2*L*alpha_p*gamma_p*gamma**2 + 2*beta*beta_p*gamma*gamma_p*L**2)** (1/2))/(2*gamma*gamma_p*abs(gamma)*abs(gamma_p))), (-(alpha*beta_p*abs (gamma)*abs(gamma_p) + alpha_p*gamma*abs(gamma)*abs(gamma_p) - L*beta*beta_p*abs(gamma)*abs(gamma_p) - L*gamma*gamma_p*abs(gamma)*abs (gamma_p) + gamma*gamma_p*(2*alpha*alpha_p*beta_p*gamma - 2*L*alpha_p*beta*beta_p*gamma + 2*L*alpha*beta_p*gamma*gamma_p + alpha**2*beta_p**2 + alpha_p**2*gamma**2 + L**2*beta**2*beta_p**2 + L**2*gamma**2*gamma_p**2 - 2*L*alpha*beta*beta_p**2 + 2*L*alpha_p*gamma_p*gamma**2 + 2*beta*beta_p*gamma*gamma_p*L**2)** (1/2))/(2*beta_p*gamma*abs(gamma)*abs(gamma_p)) + alpha_p/beta_p, (alpha*beta_p*abs(gamma)*abs(gamma_p) + alpha_p*gamma*abs(gamma)*abs (gamma_p) - L*beta*beta_p*abs(gamma)*abs(gamma_p) - L*gamma*gamma_p*abs(gamma)*abs(gamma_p) + gamma*gamma_p* (2*alpha*alpha_p*beta_p*gamma - 2*L*alpha_p*beta*beta_p*gamma + 2*L*alpha*beta_p*gamma*gamma_p + alpha**2*beta_p**2 + alpha_p**2*gamma**2 + L**2*beta**2*beta_p**2 + L**2*gamma**2*gamma_p**2 - 2*L*alpha*beta*beta_p**2 + 2*L*alpha_p*gamma_p*gamma**2 + 2*beta*beta_p*gamma*gamma_p*L**2)** (1/2))/(2*gamma*gamma_p*abs(gamma)*abs(gamma_p)))]


which, if you ignore the complexity, is a list of two items, each item is a tuple of length 2. What does this mean? I can handle the mess of the solution, but I'd like to know what is a solution for x, and for y. Why isn't it in a dictionary? Am I doing something wrong?


                thanks,

                        Brian Blais


--
Brian Blais
bbl...@bryant.edu
http://web.bryant.edu/~bblais



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