Solar System, simple

#!/usr/bin/env python
# -*- coding: utf8 -*-
dimension = 800 #(0.01 of A.U.)
dt = 0.001
delay = 1
gM = 1.
scale = 50
IterMult = 100
import numpy as np
import Tkinter
import itertools
current_time = 0
class Planet:
    def __init__(self,canv,x,y,vx,vy,mass,color,index):
        self.x = float(x)
        self.y = float(y)
        self.vx = float(vx)
        self.vy = float(vy)
        self.mass = float(mass)
        self.color = color
        self.canv = canv
        self.index = index
        self.position=self.canv.create_oval(dimension/2+int(scale*self.x)-5,dimension/2+int(scale*self.y)-5,
        dimension/2+int(scale*self.x)+5,dimension/2+int(scale*self.y)+5,fill=self.color,outline='white')
        self.energy = self.canv.create_text(100,100*(self.index+0.5),text=
        str("T+U: ")+str(0.5 * self.mass * (self.vx**2+self.vy**2)-gM * self.mass/np.sqrt(self.x**2 + self.y**2)),fill=self.color)
        self.momentum = self.canv.create_text(100,100*(self.index+0.5)+50,text=
        str("Lz: ")+str(self.x*self.vy-self.y*self.vx),fill=self.color)
    def time_step(self):
        canv.delete(self.position)
        del self.position
        canv.delete(self.energy)
        del self.energy
        canv.delete(self.momentum)
        del self.momentum
        r = np.sqrt (self.x**2 + self.y**2)
        self.energy = self.canv.create_text(100,100*(self.index+0.5),text=
        str("T+U: ")+str(0.5 * self.mass * (self.vx**2+self.vy**2)-gM * self.mass/r),fill=self.color)
        self.momentum = self.canv.create_text(100,100*(self.index+0.5)+50,text=
        str("Lz: ")+str(self.x*self.vy-self.y*self.vx),fill=self.color)
        #self.canv.create_oval(dimension/2+int(scale*self.x),dimension/2+int(scale*self.y),
        #dimension/2+int(scale*self.x),dimension/2+int(scale*self.y),fill=self.color,outline=self.color)
        self.x,self.y,self.vx,self.vy = RK4(self.x,self.y,self.vx,self.vy,dt)
        self.position=self.canv.create_oval(dimension/2+int(scale*self.x)-5,dimension/2+int(scale*self.y)-5,
        dimension/2+int(scale*self.x)+5,dimension/2+int(scale*self.y)+5,fill=self.color,outline='white')

def RK1(x,y,vx,vy,t):
    r = np.sqrt (x**2 + y**2)
    vx = vx - gM * x / r**3 * t
    vy = vy - gM * y / r**3 * t
    x = x + vx * t
    y = y + vy * t
    return x,y,vx,vy


def RK4(x,y,vx,vy,t):
    x1 = x
    y1 = y
    vx1 = vx
    vy1 = vy
    r = np.sqrt (x**2 + y**2)
    ax1 =  - gM * x / r**3
    ay1 =  - gM * y / r**3
    r1 = np.sqrt (x1**2 + y1**2)
    x2 = x + 0.5 * t * vx1
    y2 = y + 0.5 * t * vy1
    vx2 = vx - 0.5 * t * gM * x1 / r1**3
    vy2 = vy - 0.5 * t * gM * y1 / r1**3
    r2 = np.sqrt (x2**2 + y2**2)
    ax2 =  - gM * x2 / r2**3
    ay2 =  - gM * y2 / r2**3
    x3 = x + 0.5 * t * vx2
    y3 = y + 0.5 * t * vy2
    vx3 = vx - 0.5 * t * gM * x2 / r2**3
    vy3 = vy - 0.5 * t * gM * y2 / r2**3
    r3 = np.sqrt (x3**2 + y3**2)
    ax3 =  - gM * x3 / r3**3
    ay3 =  - gM * y3 / r3**3
    x4 = x + t * vx3
    y4 = y + t * vy3
    vx4 = vx - gM * x3 / r3**3 * t
    vy4 = vy - gM * y3 / r3**3 * t
    r4 = np.sqrt (x4**2 + y4**2)
    ax4 =  - gM * x4 / r4**3
    ay4 =  - gM * y4 / r4**3
    return x + t*(vx1+vx4+2*(vx2+vx3))/6.,y + t*(vy1+vy4+2*(vy2+vy3))/6.,vx + t*(ax1+ax4+2*(ax2+ax3))/6.,vy + t*(ay1+ay4+2*(ay2+ay3))/6.,


root = Tkinter.Tk()
canv = Tkinter.Canvas(root, width = dimension, height = dimension, bg = 'black')
root.attributes('-fullscreen',True)
canv.pack(expand='yes',fill='both')
canv.create_oval(dimension/2-scale/10,dimension/2-scale/10,dimension/2+scale/10,dimension/2+scale/10,fill="white",outline="white")
mercury = Planet(canv,0.459,0.,0.,1.327,0.0553,"orange",1)
venus = Planet(canv,0.716,0.,0.,1.188,0.815,"yellow",2)
earth = Planet(canv,1.00000,0.,0.,1.0,1.0,"blue",3)
mars = Planet(canv,1.6,0.,0.,0.750,0.107,"red",4)
juppiter = Planet(canv,5.369,0.,0.,0.425,317.83,"brown",5)
saturn = Planet(canv,9.957,0.,0.,0.310,95.159,"dark goldenrod",6)
uranus = Planet(canv,19.748,0.,0.,0.222,14.536,"sky blue",7)
neptune = Planet(canv,29.886,0.,0.,0.183,17.147,"royal blue",8)
#guest = Planet(canv,0.8,10,0.,-0.5,0.25,"purple",0)
system=[]
system.append(mercury)
system.append(venus)
system.append(earth)
system.append(mars)
system.append(juppiter)
system.append(saturn)
system.append(uranus)
system.append(neptune)
#system.append(guest)

timetext = canv.create_text(dimension/2,dimension/8,text=str("Time: ")+str(current_time)+str(" days"),fill='white')

def on_timer():
    global current_time, timetext
    canv.delete(timetext)
    del timetext
    current_time += 365*IterMult*dt/2/np.pi
    timetext = canv.create_text(dimension/2,dimension/8,text=str("Time: ")+str(current_time)+str(" days"),fill='white')

    for p in system:
        for _ in itertools.repeat(None, IterMult):
            p.time_step()
    root.after(delay, on_timer)
on_timer()
root.mainloop()