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# [SNIPPET_NAME: Turtle Gravity]
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# [SNIPPET_CATEGORIES: PyTurtle]
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# [SNIPPET_DESCRIPTION: Use turtle to move a moon and planet around a star.]
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# [SNIPPET_DOCS: http://docs.python.org/library/turtle.html]
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# [SNIPPET_AUTHOR: Grant Bowman <grantbow@ubuntu.com>]
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# [SNIPPET_LICENSE: PSF]
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""" turtle-example-suite:
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tdemo_planets_and_moon.py
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Gravitational system simulation using the
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approximation method from Feynman-lectures,
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p.9-8, using turtlegraphics.
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Example: heavy central body, light planet,
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Planet has a circular orbit, moon a stable
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orbit around the planet.
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You can hold the movement temporarily by pressing
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the left mouse button with mouse over the
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scrollbar of the canvas.
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from turtle import Shape, Turtle, mainloop, Vec2D as Vec
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from time import sleep
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class GravSys(object):
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for p in self.planets:
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for i in range(10000):
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for p in self.planets:
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def __init__(self, m, x, v, gravSys, shape):
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Turtle.__init__(self, shape=shape)
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gravSys.planets.append(self)
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self.gravSys = gravSys
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self.resizemode("user")
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self.v = self.v + 0.5*dt*self.a
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for planet in self.gravSys.planets:
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v = planet.pos()-self.pos()
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a += (G*planet.m/abs(v)**3)*v
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self.setpos(self.pos() + dt*self.v)
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if self.gravSys.planets.index(self) != 0:
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self.setheading(self.towards(self.gravSys.planets[0]))
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self.v = self.v + dt*self.a
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## create compound yellow/blue turtleshape for planets
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planetshape = Shape("compound")
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planetshape.addcomponent(m1,"orange")
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planetshape.addcomponent(m2,"blue")
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s.getscreen().register_shape("planet", planetshape)
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## setup gravitational system
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sun = Star(1000000, Vec(0,0), Vec(0,-2.5), gs, "circle")
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earth = Star(12500, Vec(210,0), Vec(0,195), gs, "planet")
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earth.pencolor("green")
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moon = Star(1, Vec(220,0), Vec(0,295), gs, "planet")
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moon.pencolor("blue")
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if __name__ == '__main__':
added
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pyturtle/tdemo_planet_and_moon.py
