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Is there any way to show a pyplot figure in Python 2.65, Matplotlib 0.99, without locking everything else?

I have a program with a Pmw GUI running on Python 2.75 with Matplotlib 1.3.1. on Windows (64-bit Winpython). Everytime a figure is drawn (or everytime something is added to an existing one), the routine calls plt.show(). It is possible to show pyplot figures while allowing the user to keep using the GUI and manipulate the figures, nothing blocks anything, as I want it to be since I need the user to look at the plots when deciding what to do next in the GUI, and to have several plots next to each other for comparison.

Now, I need to make all of this work on a system with Python 2.65 and Matplotlib 0.99. The behaviour now seems to be that nothing is visible unless plt.show() is called, and then it will block everything until the plot window is closed. I tried using plt.draw() instead but then the figure does not even show up. Worse: Some routines who draw into existing figures never get a chance because they can't execute while the figure is being shown, and when they can, the figure is gone already. I cannot wait until the last drawing operation because the graphs are meant to build up incremental, adding information to existing graphs which the user needs to be able to see.

I am not allowed to update matplotlib. I am allowed to use non-binary parts of libraries if I make them part of "my" software package.

Ideally, I am looking for code that will work in both environments I'm working in, but at this point I am willing to make compromises...

Update: I have found some code running in the same environment that is able to do all of these things, where I can remove the plt.show() calls, even run it in IDLE (which according to matplotlib docs has problems in these regards), and it "just works" -- I haven't been able to find any difference in how the two codes handle the task: Both define a figure.axes object, pass it to routines that draw into them (using plt.plot()) and store it for future use.

I've also found that my current code will change its behaviour on the current set of libraries, depending on how I run it: In a "regular" console in Spyder or a system console, all's fine, but on a dedicated console in Spyder, the first plot will lock up the interface

=> I'm beginning to think this isn't about the matplotlib version after all, but have no idea where else to look --is there anything else that changes matplotlib's behaviour, based on how it's launched?

Zak
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2 Answers2

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It looks like you are looking for:

plt.show(block=False)

or plt.ion:

plt.ion()
plt.show()
# update figure, calc stuff
plt.pause()

Not really sure if they are available in 0.99.

elyase
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  • unfortunately, I figured out it was introduced in 1.0 :( – Zak Jan 15 '15 at 11:43
  • Sad to hear, I hope somebody can come with a solution. – elyase Jan 15 '15 at 11:51
  • I no longer think it's due to the plt library version -- other codes can do this, and even on my development system, a different way of launching the script gives a different result (see update above). weirder and weirder... – Zak Jan 15 '15 at 12:01
  • Researching what exactly plt.ion() does is what led me to the eventual solution, so thank you! – Zak Jan 15 '15 at 12:31
  • Glad to hear it helped! – elyase Jan 15 '15 at 14:52
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elyase's answer sent me into the right direction:

import matplotlib
matplotlib.interactive(True)

This at the beginning of a script is what it takes to make sure that matplotlib will always and in all environments create plots in a way that allows scripts to continue running, while allowing the user to manipulate the figure and the code to keep drawing into it.

Matplotlib has two modes of operating: The interactive and the non-interactive, and my script going into the latter mode was the problem.

I have still no idea why this is the default behaviour in some cases and not in others (had believed it was one standard setting per matplotlib installation). Since other scripts are able to run without the above. and there must be something that my script inadvertently does to land in non-interactive mode, but the above code is what will override the setting, come what may; at least in all scenarios I've tried so far: python 2.75, matplotlib 1.3.1 using Spyder's regular and dedicated shells and system shells, and Py 2.65, matplotlib 0.99, using system shells and IDLE.

P.S.: This does not seem to help on Linux. I tried to run the same skript (Tkinter GUI that opens plots, is able to draw into existing plots) on SuSE 13.1 (current version of python 2.7 and all libraries) and no single plot window pops up until the GUI is closed, and then they all jump at me ... it seems that it's not trivial to make matplotlib behave the same everywhere.

Zak
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