How to use sympy solve in for loop

Question

I'm using sympy to solve an equation in a for loop in which at each interaction a variable (kp) multiples the function. But in each interaction the length of the output increases. I have an array k and kp is selected from k

k = [2,4,5,7,9]
for kp in k:
    didt = beta * kp * teta
    dteta = integrate(1/((kp-1) * pk * didt / avgk),teta)
    dt = integrate(1,(t,0 ,1))
    teta2 = solve(dteta - dt ,teta)
    #print(solve(dteta - dt ,teta))
    didt2 = beta *  solve(dteta - dt ,teta) *kp
    print(didt2)

Also, the output for didt2 for 1st iteration is [1.49182469764127, 1.49182469764127] for the second one is [11.0231763806416, 11.0231763806416, 11.0231763806416, 11.0231763806416] for the 3rd one is [54.5981500331442, 54.5981500331442, 54.5981500331442, 54.5981500331442, 54.5981500331442] I'm just wondering, why the length of didt2 increases at each interaction?

Answer 1

It looks like solve() returns a list. This means that beta * solve(dteta - dt ,teta) *kp doesn't do what you think. Rather than multiplying the result, you are duplicating the elements of the returned list. For a simple example, try to see what the output is:

[0] * 10

In your case, kp takes on the values of 2, 4, and 5 on each iteration of the list, so the output you see is the result of doing

[1.49182469764127] * 2
[11.0231763806416] * 4
[54.5981500331442] * 5

These all result in lists with the exact length of the value of kp. It does not do numeric multiplication.