How To Define Variable Values Using User Input

I have come across an issue I don't quite know how to solve. I'm trying to use solver to solve a simple equation. However, I want it so that you can solve for any variable you want

Solution 1:

I'm not sure but maybe this is what you want:

from sympy import *

a, b, c, d = syms = symbols('a b c d')
eq = a + (b-1) * c-d

constants=[]
input_string = '1 2 3 d'
input_words = input_string.split()
rep = {}
for word, sym inzip(input_words, [a,b,c,d]):
    if word.isalpha():
        solve_for = sym
    else:
        rep[sym] = int(word)

soln = solveset(eq.subs(rep), solve_for)

print(soln)

Basically we build up a dict and pass that to subs:

In [1]: (x + 2*y)                                                                                                                 
Out[1]: x + 2⋅y

In [2]: (x + 2*y).subs({x: 5})                                                                                                    
Out[2]: 2⋅y + 5