How could I solve the error of putting a string in the sympy set solver with an input?

Question

So I’m trying to create this program where it takes an input (for example x+2=5) and sympy solves that equation. However since I believe that "=" sign will cause an error I tried to cut it out from the input but with this I’m finding my self inputting a string type in the simpy solver. Is there any solution to this?

import math
from sympy import *

class operations():

    def __init__(self):
        self.operation = input()


    def solution(self, *o):
        x, y, z = symbols("x y z")
        equals = self.operation.split("=",1)[1]
        equation = self.operation.split("=")[0]
        solution = solveset(Eq(equation, int(equals)), x)
        print(solution)


operations().solution()

Asked By: Guilherme Santos

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Source

Answer 1

You can use sympify to convert a string to a symbolic expression, although you will have to remove the equal sign first. In the following code, first I split the string where the equal sign is found, then I convert the two resulting strings to symbolic expressions with sympify, finally I solve the equation.

def solution(self, *o):
    left, right = [sympify(t) for t in self.operation.split("=")]
    solution = solveset(left - right) # solve left - right = 0
    print(solution)

Answered By: Davide_sd

Answer 2

You can use parse_expr to parse raw strings. There are fine tuning settings that can be used, but if you are inputting a valid SymPy expressions (or nearly so) on each side of the equal sign then specifying transformations='all' is a simple way to parse the equation as an equality:

>>> from sympy.parsing import parse_expr
>>> parse_expr('2x=4', transformations='all')
Eq(2*x, 4)
>>> solveset(_)
{2}

Answered By: smichr

How could I solve the error of putting a string in the sympy set solver with an input?

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