Python 3 TypeError: unsupported operand type(s) for ** or pow(): 'str' and 'int'

Question

#Import the module
from math import sqrt

#Using while loop statement to make the program not finish before the user close the program.
while True:

#Print out the introduction message, and get the input value to solve the quadratic equation.
    print("ax^2+bx+c=0의 꼴로 된 방정식을 풀 수 있습니다. a, b, c의 값을 차례대로 입력하세요.")
    a = input("a를 입력하세요 : ")
    b = input("b를 입력하세요 : ")
    c = input("c를 입력하세요 : ")

#Define function that checks whether the input values are natural number or negative number
    def func_num(n):
        if n[0] == '-':
            n = -int(n[1:])
        else:
            n = int(n)

#Execute the function for the input value a, b, c
    func_num(a); func_num(b); func_num(c);

#This if statement chekcs whether the solution of the quadratic equation going to be real number or imaginary number.
    if b ** 2 < 4*a*c:
        solution1 = ((sqrt((b ** 2)-(4*a*c)))-b) / (2*a)
        solution2 = (-(sqrt((b ** 2)-(4*a*c)))-b) / (2*a)
    else:
        square_root = sqrt( -(b**2 - 4*a*c) ) + 1j
        solution1 = ( (square_root)  - b  ) / (2*a)
        solution2 = ( -(square_root)  - b  ) / (2*a)

#Prints out the solution of the quadratic equation.
    print("정답은 바로바로... {}, {} 이거다!".format(solution1, solution2))

but it gives an error (for any input a, b, c that are integer):

Python 3 TypeError: unsupported operand type(s) for ** or pow(): 'str' and 'int'

I think the problem is related to func_num() (because that error occurs when I do the calculation with number and strings)

But I still can't find which part is wrong.

Answer 1

The reason giving u type error is you did not store and update the variables after calling the function.

Try

 a = func_num(a)
 b = func_num(b)
 c = func_num(c)

And modify your function to return n because you only passing a copy n into the function