1 #! /usr/bin/env python

     2 

     3 # Simulate "electrons" migrating across the screen.

     4 # An optional bitmap file in can be in the background.

     5 #

     6 # Usage: electrons [n [bitmapfile]]

     7 #

     8 # n is the number of electrons to animate; default is 30.

     9 #

    10 # The bitmap file can be any X11 bitmap file (look in

    11 # /usr/include/X11/bitmaps for samples); it is displayed as the

    12 # background of the animation.  Default is no bitmap.

    13 

    14 from Tkinter import *

    15 import random

    16 

    17 

    18 # The graphical interface

    19 class Electrons:

    20 

    21     # Create our objects

    22     def __init__(self, n, bitmap = None):

    23         self.n = n

    24         self.tk = tk = Tk()

    25         self.canvas = c = Canvas(tk)

    26         c.pack()

    27         width, height = tk.getint(c['width']), tk.getint(c['height'])

    28 

    29         # Add background bitmap

    30         if bitmap:

    31             self.bitmap = c.create_bitmap(width/2, height/2,

    32                                           bitmap=bitmap,

    33                                           foreground='blue')

    34 

    35         self.pieces = []

    36         x1, y1, x2, y2 = 10,70,14,74

    37         for i in range(n):

    38             p = c.create_oval(x1, y1, x2, y2, fill='red')

    39             self.pieces.append(p)

    40             y1, y2 = y1 +2, y2 + 2

    41         self.tk.update()

    42 

    43     def random_move(self, n):

    44         c = self.canvas

    45         for p in self.pieces:

    46             x = random.choice(range(-2,4))

    47             y = random.choice(range(-3,4))

    48             c.move(p, x, y)

    49         self.tk.update()

    50 

    51     # Run -- allow 500 movemens

    52     def run(self):

    53         try:

    54             for i in range(500):

    55                 self.random_move(self.n)

    56         except TclError:

    57             try:

    58                 self.tk.destroy()

    59             except TclError:

    60                 pass

    61 

    62 

    63 # Main program

    64 def main():

    65     import sys, string

    66 

    67     # First argument is number of electrons, default 30

    68     if sys.argv[1:]:

    69         n = string.atoi(sys.argv[1])

    70     else:

    71         n = 30

    72 

    73     # Second argument is bitmap file, default none

    74     if sys.argv[2:]:

    75         bitmap = sys.argv[2]

    76         # Reverse meaning of leading '@' compared to Tk

    77         if bitmap[0] == '@': bitmap = bitmap[1:]

    78         else: bitmap = '@' + bitmap

    79     else:

    80         bitmap = None

    81 

    82     # Create the graphical objects...

    83     h = Electrons(n, bitmap)

    84 

    85     # ...and run!

    86     h.run()

    87 

    88 

    89 # Call main when run as script

    90 if __name__ == '__main__':

    91     main()