matplotlib-users Mailing List for matplotlib

On Sat, Jan 28, 2012 at 10:31 AM, Jerzy Karczmarczuk <
jer...@un...> 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

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