class Particle(object):
    
    def __init__(self, mass, x, y, z, vx, vy, vz):
        self.mass = mass
        self.x = x
        self.y = y
        self.z = z
        self.vx = vx
        self.vy = vy
        self.vz = vz
        
    def kinetic_energy(self):
        return 0.5 * self.mass * (self.vx ** 2 + self.vy ** 2 + self.vz ** 2)
    
    def separation(self, other):
        return np.sqrt((self.x - other.x) ** 2 + (self.y - other.y) ** 2 + (self.z - other.z) ** 2)
    
    def move(self, dt):
        self.x += dt * self.vx
        self.y += dt * self.vy
        self.z += dt * self.vz

p1 = Particle(1., 5.5, 4.4, 3.4, 3.4, 4.4, 7.7)
p1.kinetic_energy()

p2 = Particle(0.2, 3.3, 4.1, 3.1, -2.2, 4.4, -5.4)
p1.separation(p2)

p2.separation(p1)

p1.move(1.)
print p1.x, p1.y, p1.z

for i in range(10):
    p1.move(0.1)
    print p1.x, p1.y, p1.z

class ChargedParticle(Particle):
    def __init__(self, mass, x, y, z, vx, vy, vz, charge):
        self.charge = charge
        Particle.__init__(self, mass, x, y, z, vx, vy, vz)  # avoids having to re-define all the attributes

p3 = ChargedParticle(4., 2.2, 3.2, 4.3, 6.6, -2.3, 2.2, -1)

p3.separation(p1)

p3.charge