“未使用局部变量”（python3）

Question

Code:

#eg. point = (1,2) and eqn = (a,b,c) where the equation is ay+bx+c=0

def reflect( point, eqn ):    
    #tuples to list
    new_p = list(point)
    new_eqn = list(eqn)
    
    #sub values
    p = new_p[0]
    q = new_p[1]
    a = new_eqn[0]
    b = new_eqn[1]
    c = new_eqn[2]
    
    #formula where p'=((a^2−b^2)−2b(aq+c))/a^2+b^2
    p_new = round((p*(a**2−b**2)−2*b*(a*q+c))/(a**2+b**2),1)
    q_new = round((q*(b**2−a**2)−2*a*(b*p+c))/(a**2+b**2),1)
    
    return p_new,q_new

error:

p_new = round((p*(a**2−b**2)−2*b*(a*q+c))/(a**2+b**2),1)
                       ^
SyntaxError: invalid character in identifier

Q: Why is the character invalid? When I plug this into pycharm, I also get errors that my #sub values are not being used.

Answer 1

The "minus" symbol in your code isn't one, it is Symbole Unicode «−» (U+2212)

>> ord("−") # yours
8722
>> ord("-") # the real one
45

Fix that and it'll work

Answer 2

You should use '-' character as subtraction operator instead of '−'.