croots() was written by Tim Peters


def croots(c, n):
    """Return list of the n n'th roots of complex c."""
    from math import sin, cos, atan2, pi
    arg = abs(c)**(1.0/n)
    theta = atan2(c.imag, c.real)
    result = []
    for i in range(n):
        theta2 = (theta + 2*pi*i)/n
        x = arg * cos(theta2)
        y = arg * sin(theta2)
        result.append(complex(x, y))
    return result