Python polynomial pow

I have my own defined Polynomial class, which is in form of list of coefficients.
Something like

axˆ2 + bx + c is equals to [c, b, a]
(for ax + b == [b, a]
similarly, for axˆ3 + bxˆ2 + cx + d == [d, c, b, a])

and the len() of list depends of the index of function.

I want to define a custom __pow__ function but I really have no idea how to implement it.

Here is a function to get the coefficients of two polynomials when you multiply them together.

def multiply(a, b):
    """
        polynomials where.
        [a1, a2, a3] -> a1 + a2*x + a3*x^2
        [b1, b2, b3] -> b1 + b2*x + b3*x^2
    """
    c = [0.0]*(len(a) + len(b)-1)

    for i in range(len(a)):
        ai = a[i]
        for j in range(len(b)):
            c[i + j] += ai * b[j]

    return c


x = [1, 1]
y = [2, 1, 0]
print(multiply(x, y))

Which shows [2.0, 3.0, 1.0, 0].

Then make a pow function to call multiply in a loop.

def pow(a, n):
    """
     a^n
    """
    c = [1]
    for i in range(n):
        c = multiply(c, a)
    return c

x = [1, 1]
print(pow(x, 4))

Which outputs [1.0, 4.0, 6.0, 4.0, 1.0] as expected.