You would need some sort of atomic lock on your file to stop simultaneous
access. It looks to me as though it might be worth you looking at some sort
of inter-process communication such as passing these values over a socket.
On 4 Mar 2014 06:22, "VindRaider" <[email protected]> wrote:
> I have a text file which acts as a source for program A and sink for
> program B. Program B responsible for updating the file does so in regular
> intervals of time and always overwrite the file. Program A that is reading
> the file is constantly reading it and takes in the updated values whenever
> that happens. It works fine for sometime. But eventually, Program A
> crashes. The error shown is:
>
> File "/home/../baba_rect.py", line 61, in on_draw
> if (int(a[core_id]) <= 100):
> ValueError: invalid literal for int() with base 10: ''
>
> Here is the code for Program A:
>
> import sys, time, math, os, random
> from pyglet.gl import *
>
> red = [255,0,0]
> green = [0,255,0]
> blue = [0,0,255]
> black = [0,0,0]
>
> dim_x = 2;
> dim_y = 2;
>
> window = pyglet.window.Window()
>
> label = pyglet.text.Label('Simulation',
> font_name='Times New Roman',
> font_size=16,
> color=(204,204,0,255), #red font (255,0,0)
> opacity=255
> x=window.width, y=window.height,
> anchor_x='right', anchor_y='top')
>
> class FilledSquare:
> def __init__(self, width, height, xpos, ypos):
> self.xpos = xpos
> self.ypos = ypos
> self.angle = 0
> self.size = 1
> x = width/2.0
> y = height/2.0
> self.vlist = pyglet.graphics.vertex_list(4, ('v2f', [-x,-y, x,-y,
> -x,y, x,y]), ('t2f', [0,0, 1,0, 0,1, 1,1]))
> def draw(self,w,h,x,y):
> self.width=w
> self.height=h
> self.xpos=x
> self.ypos=y
> glPushMatrix()
> glTranslatef(self.xpos, self.ypos, 0)
> self.vlist.draw(GL_TRIANGLE_STRIP)
> glPopMatrix()
>
>
> @window.event
> def on_draw():
> window.clear()
> glClearColor(0, 0.3, 0.5, 0)
> glClear(GL_COLOR_BUFFER_BIT)
> label.draw()
>
> for i in range(0,dim_x):
> for j in range(0,dim_y):
> print i,",",j
> #read file
> f = open('r.txt', 'r')
> a = f.readline()
> a = a.rstrip('\n')
> a = a.split(" ")
> f.close()
> #core_id
> core_id = j*dim_x + i;
> if (int(a[core_id]) <= 100):
> color = red
> elif (int(a[core_id]) <= 200):
> color = green
> elif (int(a[core_id]) <= 300):
> color = blue
> else:
> color = black
>
> glColor3f(color[0], color[1],color[2])
> squares[i+j].draw(60,60,i*50+200,j*50+200)
>
> squares = [FilledSquare(30, 30, 0, 0), FilledSquare(30, 30, 0, 0),
> FilledSquare(30, 30, 0, 0), FilledSquare(30, 30, 0, 0)] # 2x2
>
> pyglet.app.run()
>
> This is how the text file *r.txt* may look like at any instant in time:
>
> 10 20 120 235
>
> I believe the reason for the crash is because at that point, it so happens
> that both Pgm A and Pgm B are accessing the file simultaneously and Pgm A
> reads a *" "* instead of the number which can't be converted to int(). If
> my conclusion is indeed true, then how can I overcome this?
>
> Or: Is it possible to make pyglet.app.run() sensitive to any change to
> *r.txt*? i.e. Pgm A runs only when there is a change in the text file,
> thus avoiding the conflict.
>
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