point3d

class Point3D:
    def __init__(self, x, y, z, r, phi, psi):
        self.x = x
        self.y = y
        self.z = z
        self.r = r
        self.phi = phi
        self.psi = psi

    @staticmethod
    def r_from_cartesian(x, y, z):
        pass

    @staticmethod
    def phi_from_cartesian(x, y, z):
        pass

    @staticmethod
    def psi_from_cartesian(x, y, z):
        pass

    @staticmethod
    def x_from_polar(r, phi, psi):
        pass

    @staticmethod
    def y_from_polar(r, phi, psi):
        pass

    @staticmethod
    def z_from_polar(r, phi, psi):
        pass

    @classmethod
    def from_cartesian(cls, x, y, z):
        r = cls.r_from_cartesian()
        phi = cls.phi_from_cartesian()
        psi = cls.psi_from_cartesian()
        return cls(x, y, z, r, phi, psi)

    @classmethod
    def from_polar(cls, r, phi, psi):
        x = cls.x_from_polar(r, phi, psi)
        y = cls.y_from_polar(r, phi, psi)
        z = cls.z_from_polar(r, phi, psi)
        return cls(x, y, z, r, phi, psi)