matplotlib Code

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@header@
<h2>Using matplotlib interactively</h2>


By default, matplotlib defers drawing until the end of the script
because drawing can be an expensive opertation, and in often you don't
want to update the plot every time a single property is changed, only
once after all the properties have changed.

But in interactive mode, eg from the python shell, you usually do want
to update the plot with every command, eg, after changing the xlabel
or the marker style of a line.  With the <a
href=backends.html#TkAgg>TkAgg</a> backend, you can use matplotlib
from an arbitrary python shell.  Just set TkAgg to be your default
backend and interactive to be True in your <a
href=.matplotlibrc>matplotlibrc</a> file and fire up python.  Then

<pre>
>>> from matplotlib.matlab import *
>>> plot([1,2,3])
>>> xlabel('hi mom')
</pre>

should work out of the box.  Note, in batch mode, ie when making
figures from scripts, interactive mode can be slow since it redraws
the figure with each command.  So you may want to think carefully
before making this the default behavior.  TkAgg sets interactive mode
to True when you issue the <a
href=matplotlib.matlab.html#-show>show</a> command.<p>

Unfortunately, due to the 'mainloop' cycle of GUI toolkits, it is not
yet possible to use matplotlib from an arbitrary python shell with the
other GUI backends.  Instead, there are custom solutions depending on
the GUI environment in which you use matplotlib.<p>


<h3>WX</h3> 

With a WX shell, such as pycrust, you need to put matplotlib in
interactive mode.  

<pre>
  >>> import matplotlib
  >>> matplotlib.interactive(True)
  >>> matplotlib.use('WX') 
  >>> from matplotlib.matlab import *
  >>> plot([1,2,3])
  >>> xlabel('time (s)')
</pre>

If you primarily want to use matplotlib interactively in a wx shell,
set the following in your <a href=.matplotlibrc>.matplotlibrc</a> file

<pre>
backend      : Wx
interactive  : True     
</pre>

<h3>GTK</h3> 

In the examples dir of the src distribution, there is an interactive
shell for pygtk.  It sets the interactive property for you, and
imports all the commands from matplotlib.matlab, so you can just start
plotting away <a
href=examples/interactive2.py>interactive2.py</a>).<p>

<pre>
examples> ./interactive2.py
>>> plot([1,2,3])
</pre>

<tt>interactive2.py</tt> will work with any pygtk 1.99.16 or
later, regardless of whether threading was built in or not.
<tt>interactive.py</tt> requires an interpreter with threading an
so requires a bit more work.  There are relative strengths of both
these interpreters and neither is perfect.  For example,
interactive2.py is easier to set up since it doesn't require
threading, and looks nicer, but interactive.py better handles cutting
and pasting of code blocks from an editor into the interpreter.<p>


<h2>pygtk with threading</h2>

The rest of this page details how to get pygtk setup with threading if
you want to use interactive.py (interactive2.py doesn't require it).
The core functionality of this interpreter was provided by <a
href=http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/65109>Brian
McErlean and John Finlay</a>.<p>


<h3>WIN32 Users</h3>

  You will need pygtk compiled for threading.  The lastest version for
  windows at Cedirc's website, pygtk-2.0.0 has threading built in
  automatically.  If for some reason, you need an older version, a
  windows installer for pygtk-1.99.16 with threading is available at
  <a
  href=http://nitace.bsd.uchicago.edu:8080/Wikis/Leo/Python/win32/pygtk-1.99.16.threading.win32-py2.2.exe>pygtk-1.99.16
  with threading</a>.<p>


  I have seen reports of threading difficulties with pygtk on win32,
  but haven't experienced them myself.  If you experience freezes or
  other strangeness, check the <a
  href=http://www.async.com.br/faq/pygtk/index.py?req=show&file=faq21.003.htp>pygtk
  FAQ entry</a>.<p>


<h3>Linux/UNIX Users</h3>

  To compile pygtk with threading, you need to build with<p>

  <pre>
  > python setup.py build --enable-threading
  > python setup.py install
  </pre>

  If after this install, threading still is not working for you, you
  may want to try a clean install using configure.  See below.<p>
  
<h3>Testing threading</h3>

  To test whether this install worked, try running this script<p>

  <pre>
    import pygtk
    pygtk.require('2.0')
    import gtk

    import threading, time

    def func():
      n = 0
      while 1:
        print n
        n += 1
        time.sleep(0.1)

    gtk.threads_init()
    threading.Thread(target=func).start()
    gtk.mainloop()
  </pre>


  If it spits numbers back at you, you're golden.<p>

<h3>Testing with matplotlib</h3>

  You should be able to make a simple plot with<p>

  <pre>
  > cd examples
  > ./interactive.py
  >>> plot([1,2,3])
  </pre>


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