matplotlib-users

[Matplotlib-users] Matplotlib/Pylab... A Couple Of Problems...

[<and...@ti...>]

Hello NG,

    first of all, I would like to thank you a for your kind support. I ca=
me
across a couple of problems using Matplotlib/Pylab, and I would like to
ask if someone else has encountered them or if I am missing something.

First of all, I am on a WinXP, with:
- Python 2.3.4
- wxPython 2.5.3.1
- Numeric 23.7
- I use WXAgg
- Matplotlib/Pylab 0.72.1

Problem 1:
I have downloaded the examples at:
 
http://matplotlib.sourceforge.net/matplotlib_examples_0.72.zip

If, for example, I try to run the keypress_demo.py, and if I resize the
window "too fast" (but it's not really fast, is just a normal resize), I
get an unhandled exception like:

"An unhandled exception occurred. Press "Abort" to terminate the program,=

"Retry" to exit the program normally and "Ignore" to try to continue."

No matter which is my choice, the window crashes and I get the usual XP
message about sending error messages to Microsoft and so on. It is a stra=
nge
exception, if I resize the window VERY slowly, there is no exception (usu=
ally).

Problem 2:
Considering always the keypress_demo.py, if I run it (without resizing th=
e
window ;-) ) and I press the key "g" (for the grid), the grid appears and=

suddenly disappears. I opened the keypress_demo.py and I commented out th=
e
draw() command (that follows the grid() command), and now the grid does
not disappear. What could be the problem with draw()?!? I have to use it
in my application, but I am not able to display the grid...

Thank your for every suggestion, and sorry for the long post.

Andrea.

Re: [Matplotlib-users] Matplotlib/Pylab... A Couple Of Problems...

[John H. <jdh...@ac...>]

>>>>> "andrea" == andrea gavana <and...@ti...> writes:

    andrea> No matter which is my choice, the window crashes and I get
    andrea> the usual XP message about sending error messages to
    andrea> Microsoft and so on. It is a strange exception, if I
    andrea> resize the window VERY slowly, there is no exception
    andrea> (usually).

There is a known bug in Agg on Windows XP that appears on repeated
draws (resizing does this) that causes a segmentation fault.  I've
only seen this in the context of draw markers (eg

  plot(x,y,'o') 

where 'o' is a plot marker symbol.  Do you have markers in your plot?

Unfortunately, even though I think I know where the bug is occurring,
I don't yet have a fix for it.  If it is too annoying, you may want to
roll back to 0.71 until I figure this one out.


    andrea> Problem 2: Considering always the keypress_demo.py, if I
    andrea> run it (without resizing the window ;-) ) and I press the
    andrea> key "g" (for the grid), the grid appears and suddenly
    andrea> disappears. I opened the keypress_demo.py and I commented
    andrea> out the draw() command (that follows the grid() command),
    andrea> and now the grid does not disappear. What could be the
    andrea> problem with draw()?!? I have to use it in my application,
    andrea> but I am not able to display the grid...


Oh, I get it :-)

the 'g' key is now a default part of matplotlib -- eg pressing 'g'
toggles the grid on any axes.  I wrote the keypress_demo before making
this behavior default, so what you see in the demo is that you toggle
grid two times in keypress_demo, once in the default axes handling,
and once in the demo.  And so it ends up turning it on and back off.
Time to update the demo!

    andrea> Thank your for every suggestion, and sorry for the long
    andrea> post.

Bug reports are always welcome -- thanks!

JDH