Question

I am looking for a way to add together multiple mathematical functions before assigning the numerical values for the variables in the equations.
I am doing it this way because I need to optimize my code, and I want to assign different values to the variables each time. An example of what I am trying to do:

1. f(x, y) = x + 2y

2. g(x, y) = 3x - y

3. adds f(x, y) + g(x, y) to get h(x, y), so f(x, y) + g(x, y) = h(x, y) = 4x + y

4. Now that I have h(x, y), I need multiple values from h(x, y)

x = 4; y = 3, h(x, y) = 19
x = 1, y = 0, h(x, y) = 4

etc.

Is this possible? I was trying to create them as strings, add the strings, then remove the quotes to evaluate the sum but this did not work. I am trying to do my method this way because I want to optimize my code. It would help very much if I am able to create my final function before evaluating it (it would be h(x, y) in this case).

EDIT: I’m doing additions of (e ** (x + y)), so linear solutions using matrices don’t work :/

Answer 1

SymPy can do this:

import sympy as sym

x, y = sym.symbols('xy')
f = x + 2*y
g = 3*x - y
h = f + g

This shows that SymPy has simplified the expression:

print(h)
# y + 4*x

And this shows how you can evaluate h as a function of x and y:

print(h.subs(dict(x=4, y=3)))
# 19
print(h.subs(dict(x=1, y=0)))
# 4