On Sep 20, 2010, at 7:43 PM, Benjamin Root wrote:
> On Mon, Sep 20, 2010 at 5:12 PM, Brian Blais <bbl...@bryant.edu> wrote:
> I am trying to do some simple calculations in a loop, and draw a plot
> periodically within the loop, and the drawing is not updating. I'm using the
> Enthought Python Distribution which is using Matplotlib 0.99.3 with python
> 2.6.5 on Snow Leopard, OSX 10.6.4, and am running it in ipython with the
> -pylab flag (and I've tried with the -wthread flag too). A sample piece of
> code below. It is actually drawing, because when I control-C to stop, it
> shows the plot.
>
> from pylab import *
> from numpy import *
> import sys
>
> def dot():
> sys.stdout.write('.')
> sys.stdout.flush()
>
> def busy_loop():
>
> for i in range(1000):
> r=rand(100,100)
>
> return r
>
> for t in range(1000):
>
> r=busy_loop()
>
> clf()
> imshow(r,interpolation='nearest',cmap=cm.gray)
> draw()
> show()
>
> dot()
>
> First, I would suggest using time.sleep() to do your busy loop:
>
> >>> import time
> >>> time.sleep(0.1)
>
I tried that before (even upping to 1 second)...no dice.
>
> Second, you have the show() function within the loop. Call the show()
> function only once (in interactive mode), and draw() can be used to update
> the graph.
also done...no effect.
> Also note that some plotting functions return objects that have a function
> like "update_data" that would allow you to modify the plot without having to
> call clf().
sure, but that take more effort, and I don't really care about a slow down,
because most of my time is spent in the busy loop. I do care about it
displaying *at all*, which is the problem. I am familiar with the efficient
way of animating, but for most things I want to focus on the computation and
then display here and there, so I want the shortest, clearest plotting code
without any optimizations. if I call plot commands, and then a draw, I expect
it to actually pause right there until it is done drawing, and then
continue...it's not doing that.
another wrinkle: If I run ipython -pylab, and then run my script like:
run do_my_script
I get no plot showing (an empty figure window shows, with a busy process
"rainbow spiral). Now, I control-C and the plots come up and my script stops.
I then type again:
run do_my_script
it works! once the figure is drawn once, it seems to work just fine. the
*first* time it doesn't display, and requires a control-C. weird!
can anyone reproduce this?
bb
--
Brian Blais
bbl...@bryant.edu
http://web.bryant.edu/~bblais
http://bblais.blogspot.com/
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