On Sat, Jan 28, 2012 at 10:31 AM, Jerzy Karczmarczuk <
jerzy.karczmarc...@unicaen.fr> wrote:
> Benjamin Root about my miserable event problem :
>
> Still not sure why my suggestion would not work:
>
>
> http://matplotlib.sourceforge.net/api/cbook_api.html#matplotlib.cbook.CallbackRegistry
>
>
> I thought I told you. Probably I am doing something utterly false, but my
> distilled problem is that* I am generating events from within a callback*.
> Here you are a complete skeleton program.
>
>
> from pylab import *
> from matplotlib.cbook import *
> from matplotlib.widgets import Button
> fig=figure()
> ax = fig.add_subplot(1,1,1)
> xis=axis([0,1,0,1])
> subplots_adjust(left=0.1, bottom=0.1)
> clrax = axes([0.67, 0.02, 0.08, 0.04])
> clbut = Button(clrax, 'Clear', color="1.0")
> goax = axes([0.88, 0.02, 0.08, 0.04])
> gobut = Button(goax, 'Go', color="#40ffa0")
> cbacks = CallbackRegistry()
>
> def line(*evt):
> plot(rand(2),rand(2)) ; draw()
> cbacks.process('line_', None)
>
> linv = cbacks.connect('line_', line)
>
> def clr(ev=None): del ax.lines[:]
> clbut.on_clicked(clr)
> def start(evt): cbacks.process('line_', None)
> gobut.on_clicked(start)
>
> subplot(1,1,1)
> show()
>
> The function line() is the main iterative engine, a "loop" without
> looping. It should post an event which re-launches it, and still leaving
> the master loop active, so I can clear the figure.
>
> Nope. This is a *recursive call*.
> Python bombs after a while, recursive limit exceeded, and only then the
> Clear button wakes up.
>
> Thank you for your effort.
>
> Jerzy
>
>
Jerzy,
So, where is your terminating condition? Of course it will continuously
call itself if you have nothing to stop it. Protect that call to "process"
with some sort of if-statement and use "evt" to carry some sort of state
that can be tested in that if-statement.
For example, I modified your example to use "evt" to carry an integer. The
call to process() is protected by an if-statement that checks to see if evt
is less than 10, and the call to process passes "evt + 1". The initial
call to process passes a value of zero. The program then produces 10
random lines just fine when I press "Go".
Does that help clear up your problem?
Ben Root
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