matplotlib-users Mailing List for matplotlib

Darren Dale wrote:
> On Saturday 11 August 2007 8:15:41 am Xavier Gnata wrote:
> 
>> Hi,
>>
>> Using pylab svn, the qt backend is broken.
>>
>> import pylab fails :
>>
>> /usr/lib/python2.4/site-packages/matplotlib/backends/backend_qtagg.py
>> 11
>> 12 from backend_agg import FigureCanvasAgg
>> ---> 13 from backend_qt import qt, FigureManagerQT, FigureCanvasQT,\
>> 14 show, draw_if_interactive, backend_version, \
>> 15 NavigationToolbar2QT
>>
>> /usr/lib/python2.4/site-packages/matplotlib/backends/backend_qt.py
>> 15 from matplotlib.widgets import SubplotTool
>> 16
>> ---> 17 import qt
>> 18
>> 19 backend_version = "0.9.1"
>>
>> ImportError: No module named qt
>> 
>
> That means you dont have PyQt-3 installed on your machine.
>
> 
>> If I replace import qt by import PyQt4
>> 
>
> dont!
>
> 
>> , I get another error : 
>> 
>
> If you want to use PyQt4, you should set your backend to qt4agg instead of 
> qtagg.
> 
OK my matplotlibrc was out of date. Now it works but I have found 
another but playing with the sliders of the backend:
As the log is quite long, here are only the most relevant parts :
imshow(a)
Out[7]: <matplotlib.image.AxesImage instance at 0xb262a8cc>
(play with the sliders of the qt4agg backend)
In [8]: 
---------------------------------------------------------------------------
exceptions.ValueError Python 2.4.4: 
/usr/bin/python
 Mon Aug 13 00:58:56 2007
A problem occured executing Python code. Here is the sequence of function
calls leading up to the error, with the most recent (innermost) call last.
/usr/lib/python2.4/site-packages/matplotlib/backends/backend_qt4.py in 
funcleft(self=<matplotlib.backends.backend_qt4.SubplotToolQt object>, 
val=900)
/usr/lib/python2.4/site-packages/matplotlib/figure.py in 
update(self=<matplotlib.figure.SubplotParams instance>, 
left=0.90000000000000002, bottom=None, right=None, top=None, 
wspace=None, hspace=None)
 71 self._update_this('top', top)
 72 self._update_this('wspace', wspace)
 73 self._update_this('hspace', hspace)
 74
 75 def reset():
 76 self.left = thisleft
 77 self.right = thisright
 78 self.top = thistop
 79 self.bottom = thisbottom
 80 self.wspace = thiswspace
 81 self.hspace = thishspace
 82
 83 if self.validate:
 84 if self.left>=self.right:
 85 reset()
---> 86 raise ValueError('left cannot be >= right')
 global ValueError = undefined
 87
 88 if self.bottom>=self.top:
 89 reset()
 90 raise ValueError('bottom cannot be >= top')
 91
 92
 93
 94 def _update_this(self, s, val):
 95 if val is None:
 96 val = getattr(self, s, None)
 97 if val is None:
 98 key = 'figure.subplot.' + s
 99 val = rcParams[key]
 100
 101 setattr(self, s, val)
ValueError: left cannot be >= right
**********************************************************************
Oops, IPython crashed. We do our best to make it stable, but...
It looks like that the ranges of the sliders are checked in a wrong way. 
It may be due to numerical rounding issues.
Xavier
....

Also, after looking at the embedded_tk example, it seems that you end the
script with a tk.mainloop() which kind of defeats my whole purpose, as I
need the script to keep checking for changes on a file.
What it seems that I need is some why to trigger the gui loop, but also to
have an "event" be trigged every few seconds, and that event would be
responsible for checking if there is new data, reading the file, and
updating the plot if necessary.
Is there some way to accomplish something like this?
Thanks,
Angel
---------- Forwarded message ----------
From: Angel Ezquerra Moreu <ang...@gm...>
Date: Aug 12, 2007 11:01 PM
Subject: Re: [Matplotlib-users] Cannot maximize figure while script is
running
To: mat...@li...
> I would suggest not using the pylab interface. Try building off of one of
the
> embedding_in examples in
> http://matplotlib.sourceforge.net/matplotlib_examples_0.90.0.zip.
Thank you for the answer, Darren. However, could you explain a bit more in
detail why is not a good idea to use the pylab interface? It is very simple
and easy to use (I am a Matlab user as well) so it felt very natural to try
to use it.
Angel
P.S.- Thanks for the os.path.getmtime tip.

> I would suggest not using the pylab interface. Try building off of one of
the
> embedding_in examples in
> http://matplotlib.sourceforge.net/matplotlib_examples_0.90.0.zip.
Thank you for the answer, Darren. However, could you explain a bit more in
detail why is not a good idea to use the pylab interface? It is very simple
and easy to use (I am a Matlab user as well) so it felt very natural to try
to use it.
Angel
P.S.- Thanks for the os.path.getmtime tip.

On Sunday 12 August 2007 3:56:14 am Angel Ezquerra Moreu wrote:
> Hi,
>
> I want to make a small python script that monitors a text file and plots
> its contents. This script is meant to run in Windows. The file that is
> being monitored has one floating point number per line and new numbers can
> be appended to the end of the file at any moment by some external program.
>
> Therefore the script needs to keep reading the file and if new data is
> found, it should update the plot (a simple plot() command will do for now).
> To do so the script has an endless loop that tries to read new data and if
> it can it plots it and issues a pylab.draw() command.
>
> I got the script working, (based on the "anim.py" example from the
> Matplotlib web page: http://matplotlib.sourceforge.net/examples/anim.py).
> The script updates the plot correctly when new data is added to the file.
> However, the figure itself is not really functional. By that I mean that
> the figure cannot maximized while the script is running. It is not possible
> to change the zoom or use the toolbar either.
>
> The example script has the same problem (i.e. the figure cannot maximized),
> so I'd like to know if there is any way around this or if I should use
> something other than pylab instead.
I would suggest not using the pylab interface. Try building off of one of the 
embedding_in examples in 
http://matplotlib.sourceforge.net/matplotlib_examples_0.90.0.zip.
Also, rather than repeatedly reading your data file to determine when new data 
is available, I suggest using os.path.getmtime.
Darren

Hi,
I want to make a small python script that monitors a text file and plots its
contents. This script is meant to run in Windows. The file that is being
monitored has one floating point number per line and new numbers can be
appended to the end of the file at any moment by some external program.
Therefore the script needs to keep reading the file and if new data is
found, it should update the plot (a simple plot() command will do for now).
To do so the script has an endless loop that tries to read new data and if
it can it plots it and issues a pylab.draw() command.
I got the script working, (based on the "anim.py" example from the
Matplotlib web page: http://matplotlib.sourceforge.net/examples/anim.py).
The script updates the plot correctly when new data is added to the file.
However, the figure itself is not really functional. By that I mean that the
figure cannot maximized while the script is running. It is not possible to
change the zoom or use the toolbar either.
The example script has the same problem (i.e. the figure cannot maximized),
so I'd like to know if there is any way around this or if I should use
something other than pylab instead.
Thanks!
Angel