Tool for finding modular inverses for me to make CS70 questions 😄

reed_solomon.py

class rs():
    def __init__(self, p):
        self.p = p # set the Galois Field

    def divide(self, a, b):
        a %= self.p
        b %= self.p
        b_mod_inv = 0 if b % self.p == 0 else self.find_mod_inv(b)
        return (a*b_mod_inv) % self.p

    def find_mod_inv(self, x):
        p = self.p
        x %= p
        for i in range(1, p):
            if 1 == ((x*i) % p):
                return i
        raise InverseNotFoundException("Could not find inverse for " + str(x) + " in moduli " + str(p))


class InverseNotFoundException(Exception):
    pass