variable length rolling hash python

"""
My attempt at variable length rolling hash https://www.youtube.com/watch?v=w6nuXg0BISo
"""

class VariableLengthRollingHash():

    def __init__(self, base=257, prime=1000000007):
        self.base = base
        self.prime = prime
        self.base_inverse = pow(base, prime-2, prime)
        self.max_base = self.base_inverse
        self.u_mod_p = 0

    def hash(self):
        return self.u_mod_p

    def append(self, val):
        if len(val) > 1:
            for v in val:
                self.append(v)
            return
        self.u_mod_p = (self.u_mod_p * self.base + ord(val)) % self.prime
        self.max_base = (self.max_base * self.base) % self.prime
        # print('a %s  --------- %s' % (self.u_mod_p, self.max_base))

    def skip(self, val):
        if len(val) > 1:
            for v in val:
                self.skip(v)
            return
        self.u_mod_p = (self.u_mod_p - ord(val) * self.max_base) % self.prime
        self.max_base = (self.max_base * self.base_inverse) % self.prime
        # print('s %s  --------- %s' % (self.u_mod_p, self.max_base))

    def reset(self):
        self.u_mod_p = 0
        self.max_base = self.base_inverse


def test(str1, str2):
    r1 = VariableLengthRollingHash()
    r2 = VariableLengthRollingHash()

    for l1, l2 in zip(str1, str2):
        r1.append(l1)
        r2.append(l2)

    return r1.hash() == r2.hash()

if __name__ == '__main__':
    assert not test('apple', 'applz')
    assert test('apple', 'apple')

    b = VariableLengthRollingHash()
    b.append('hello')
    n = VariableLengthRollingHash()
    n.append('zhell')

    assert not b.hash() == n.hash()
    n.skip('z')
    assert not b.hash() == n.hash()
    n.append('o')
    assert b.hash() == n.hash()
    print('Test success')