# Particle class example used to simulate diffusion of molecules

import simplegui

import random

# global constants

WIDTH = 600

HEIGHT = 400

PARTICLE_RADIUS = 5

COLOR_LIST = ["Red", "Green", "Blue", "White"]

DIRECTION_LIST = [[1,0], [0, 1], [-1, 0], [0, -1]]

# definition of Particle class

class Particle:

# initializer for particles

def __init__(self, position, color):

self.position = position

self.color = color

# method that updates position of a particle

def move(self, offset):

self.position[0] += offset[0]

self.position[1] += offset[1]

# draw method for particles

def draw(self, canvas):

canvas.draw_circle(self.position, PARTICLE_RADIUS, 1, self.color, self.color)

# string method for particles

def __str__(self):

return "Particle with position = " + str(self.position) + " and color = " + self.color

# draw handler

def draw(canvas):

for p in particle_list:

p.move(random.choice(DIRECTION_LIST))

for p in particle_list:

p.draw(canvas)

# create frame and register draw handler

frame = simplegui.create_frame("Particle simulator", WIDTH, HEIGHT)

frame.set_draw_handler(draw)

# create a list of particles

particle_list = []

for i in range(100):

p = Particle([WIDTH / 2, HEIGHT / 2], random.choice(COLOR_LIST))

particle_list.append(p)

# start frame

frame.start()