[Matplotlib-users] Beginner questions about OO interface

Mon Nov 16 12:42:11 EST 2015

David,

I should point out that Sandro's book is fairly old and that there is a new
one that replaces it: "Mastering Matplotlib". Note that neither book really
goes into any details about embedding figures into GUIs.

Ben

On Mon, Nov 16, 2015 at 12:37 PM, David Aldrich <David.Aldrich at emea.nec.com>
wrote:

> Hi Benjamin
>
>
>
> Thanks for your reply.  I have looked at your book on Amazon but thought I
> should go for Sandro Tosi’s book initially, just to learn the basics of
> Matplotlib.  Perhaps I can get yours later J
>
>
>
> Best regards
>
>
>
> David
>
>
>
> *From:* Benjamin Root [mailto:ben.v.root at gmail.com]
> *Sent:* 16 November 2015 17:23
> *To:* David Aldrich <David.Aldrich at EMEA.NEC.COM>
> *Cc:* matplotlib-users at python.org
> *Subject:* Re: [Matplotlib-users] Beginner questions about OO interface
>
>
>
> Hello David,
>
>
>
> On Mon, Nov 16, 2015 at 5:55 AM, David Aldrich <David.Aldrich at emea.nec.com>
> wrote:
>
> Hi
>
>
>
> I am new to Matplotlib and am struggling a bit to differentiate between
> the OO and pyplot interfaces.  I’m actually working with the Kivy GUI
> framework and trying to plot 4 subplots on a single figure, to be displayed
> by Kivy.  Here’s a snippet of my code:
>
>
>
> def create_plot(self):
>
>
>
>         self.fig, ((self.ax0, self.ax1), (self.ax2, self.ax3)) =
> plt.subplots(nrows=2, ncols=2)
>
>
>
>         self.ax0.set_title("A")
>
>         self.ax0.grid(True, lw = 2, ls = '--', c = '.75')
>
>
>
>         self.ax1.set_title("B")
>
>         self.ax1.grid(True, lw = 2, ls = '--', c = '.75')
>
>
>
>         self.ax2.set_title("C")
>
>         self.ax2.grid(True, lw = 2, ls = '--', c = '.75')
>
>
>
>         self.ax3.set_title("D")
>
>         self.ax3.grid(True, lw = 2, ls = '--', c = '.75')
>
>
>
>         #plt.tight_layout()
>
>         plt.show()
>
>
>
>         canvas = self.fig.canvas
>
>         self.add_widget(canvas)
>
>
>
> What worries me is that I am calling plt methods and assigning the results
> to my objects.  Is plt the state machine interface and not the OO
> interface, or is this OK?
>
>
>
> Indeed, plt is the state machine interface, and it isn't exactly the same
> thing to say "plt.show()" and to show a particular figure. You can call
> `self.fig.show()`, though.
>
>
>
>
>
> Secondly, I want to periodically update the plotted lines, so I have a
> plot method that does this:
>
>
>
>     def plot(self,  xCoords, yCoords):
>
>
>
>         if len(self.ax0.lines) > 0:
>
>             self.ax0.lines.pop(0)
>
>
>
>         line = self.ax0.plot(xCoords, yCoords, color='blue')
>
>
>
>         canvas = self.fig.canvas
>
>         canvas.draw()
>
>
>
> Does that look ok?  Can I just pop the existing line, or should I reuse
> the existing line?
>
>
>
> That would work, but it is very inefficient. Most matplotlib artist
> objects have some sort of "set_data()" or "set_offsets()" method that would
> let you update the data contained in the artist. See the following
> animation example:
> http://matplotlib.org/examples/animation/animate_decay.html
>
>
>
>
>
> Lastly, and most difficult, if I enable:
>
>
>
> plt.tight_layout()
>
>
>
> I get an exception:
>
>
>
> C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\matplotlib\tight_layout.py:225:
> UserWarning: tight_layout : falling back to Agg renderer
>
>    warnings.warn("tight_layout : falling back to Agg renderer")
>
>  Traceback (most recent call last):
>
>    File "main.py", line 1117, in <module>
>
>      GuiApp().run()
>
>    File
> "C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\kivy\app.py",
> line 801, in run
>
>      self.load_kv(filename=self.kv_file)
>
>    File
> "C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\kivy\app.py",
> line 598, in load_kv
>
>      root = Builder.load_file(rfilename)
>
>    File
> "C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\kivy\lang.py",
> line 1801, in load_file
>
>      return self.load_string(data, **kwargs)
>
>    File
> "C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\kivy\lang.py",
> line 1880, in load_string
>
>      self._apply_rule(widget, parser.root, parser.root)
>
>    File
> "C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\kivy\lang.py",
> line 2038, in _apply_rule
>
>      self._apply_rule(child, crule, rootrule)
>
>    File
> "C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\kivy\lang.py",
> line 2037, in _apply_rule
>
>      self.apply(child)
>
>    File
> "C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\kivy\lang.py",
> line 1924, in apply
>
>      self._apply_rule(widget, rule, rule)
>
>    File
> "C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\kivy\lang.py",
> line 2038, in _apply_rule
>
>      self._apply_rule(child, crule, rootrule)
>
>    File
> "C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\kivy\lang.py",
> line 2038, in _apply_rule
>
>      self._apply_rule(child, crule, rootrule)
>
>    File
> "C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\kivy\lang.py",
> line 2035, in _apply_rule
>
>      child = cls(__no_builder=True)
>
>    File "C:\SVNProj\Raggio\trunk\hostconsole\gui\mygraph.py", line 127, in
> __init__
>
>      self.create_plot()
>
>    File "C:\SVNProj\Raggio\trunk\hostconsole\gui\mygraph.py", line 224, in
> create_plot
>
>      self.add_widget(canvas)
>
>    File
> "C:\Kivy-1.9.0-py3.4-win32-x64\Python34\lib\site-packages\kivy\uix\boxlayout.py",
> line 211, in add_widget
>
>      widget.bind(
>
>  AttributeError: 'FigureCanvasAgg' object has no attribute 'bind'
>
>
>
> Can anyone help with that please?
>
>
>
> tight_layout() isn't the issue here (well, directly). The issue is that
> the canvas object that you added as a widget is not a widget as far as Kivy
> is concerned. It doesn't subclass anything that Kivy recognizes as a
> widget. By its very nature, FigureCanvasAgg is completely independent of
> any GUI frameworks. You would need to have selected the appropriate backend
> for matplotlib to use prior to importing pyplot (I don't know which one
> Kivy is compatible with, GTK? QT? something else?).
>
> By the way, chapter 5 of my book, "Interactive Applications Using
> Matplotlib" goes into detail explaining the ins and outs of GUI embedding
> with matplotlib. While I don't cover Kivy, I do a Rosetta Stone-like
> explanation covering GTK, Qt4, Wx, and Tk, and I explain the general
> concepts. Perhaps it might be useful?
>
>
> http://www.amazon.com/Interactive-Applications-using-Matplotlib-Benjamin/dp/1783988843/
>
> Cheers!
>
> Ben Root
>
>
>
>
>
>
> Best regards
>
>
>
> David
>
>
> _______________________________________________
> Matplotlib-users mailing list
> Matplotlib-users at python.org
> https://mail.python.org/mailman/listinfo/matplotlib-users
>
>
>
>
>
> Click here
> <https://www.mailcontrol.com/sr/hMR6wrmFxrHGX2PQPOmvUg5!3elP1qzzXT9AmZTFOf3PtdjRxp3YcZ022EfPgnJAeE0+ZrrokCngE3KctAewCA==>
> to report this email as spam.
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/matplotlib-users/attachments/20151116/403a1576/attachment-0001.html>