Staging
v0.5.1
v0.5.1
https://github.com/python/cpython
Tip revision: fb0928d1176a1e517cc5e46aeafbf54ff5c2554c authored by Barry Warsaw on 09 March 2010, 22:31:52 UTC
Bumping to 2.6.5rc2
Bumping to 2.6.5rc2
Tip revision: fb0928d
tdemo_planet_and_moon.py
#!/usr/bin/python
""" turtle-example-suite:
tdemo_planets_and_moon.py
Gravitational system simulation using the
approximation method from Feynman-lectures,
p.9-8, using turtlegraphics.
Example: heavy central body, light planet,
very light moon!
Planet has a circular orbit, moon a stable
orbit around the planet.
You can hold the movement temporarily by pressing
the left mouse button with mouse over the
scrollbar of the canvas.
"""
from turtle import Shape, Turtle, mainloop, Vec2D as Vec
from time import sleep
G = 8
class GravSys(object):
def __init__(self):
self.planets = []
self.t = 0
self.dt = 0.01
def init(self):
for p in self.planets:
p.init()
def start(self):
for i in range(10000):
self.t += self.dt
for p in self.planets:
p.step()
class Star(Turtle):
def __init__(self, m, x, v, gravSys, shape):
Turtle.__init__(self, shape=shape)
self.penup()
self.m = m
self.setpos(x)
self.v = v
gravSys.planets.append(self)
self.gravSys = gravSys
self.resizemode("user")
self.pendown()
def init(self):
dt = self.gravSys.dt
self.a = self.acc()
self.v = self.v + 0.5*dt*self.a
def acc(self):
a = Vec(0,0)
for planet in self.gravSys.planets:
if planet != self:
v = planet.pos()-self.pos()
a += (G*planet.m/abs(v)**3)*v
return a
def step(self):
dt = self.gravSys.dt
self.setpos(self.pos() + dt*self.v)
if self.gravSys.planets.index(self) != 0:
self.setheading(self.towards(self.gravSys.planets[0]))
self.a = self.acc()
self.v = self.v + dt*self.a
## create compound yellow/blue turtleshape for planets
def main():
s = Turtle()
s.reset()
s.tracer(0,0)
s.ht()
s.pu()
s.fd(6)
s.lt(90)
s.begin_poly()
s.circle(6, 180)
s.end_poly()
m1 = s.get_poly()
s.begin_poly()
s.circle(6,180)
s.end_poly()
m2 = s.get_poly()
planetshape = Shape("compound")
planetshape.addcomponent(m1,"orange")
planetshape.addcomponent(m2,"blue")
s.getscreen().register_shape("planet", planetshape)
s.tracer(1,0)
## setup gravitational system
gs = GravSys()
sun = Star(1000000, Vec(0,0), Vec(0,-2.5), gs, "circle")
sun.color("yellow")
sun.shapesize(1.8)
sun.pu()
earth = Star(12500, Vec(210,0), Vec(0,195), gs, "planet")
earth.pencolor("green")
earth.shapesize(0.8)
moon = Star(1, Vec(220,0), Vec(0,295), gs, "planet")
moon.pencolor("blue")
moon.shapesize(0.5)
gs.init()
gs.start()
return "Done!"
if __name__ == '__main__':
msg = main()
print msg
mainloop()