Threading - Matplotlib - main thread is not in main loop - Tcl_AsyncDelete

[Martin Fayad]

Hey guys. I have a problem. I made a GUI in which you SETS parameters for Matplotlib graph and then with a START Button a new Thread is started and this Thread opens/creates a Matplotlib-Graph outside the GUI(not as a widget).

The reason i use new thread is that I dont want to have frozen GUI while the Graph window is open

Everything works fine. But as a rule, everytime i close the GUI, python post this or only part of the error shown below. Thats not really a problem as it is after closing the GUI. What is a problem is that the GUI everytime after some time crashes giving similar or same error:

 Exception ignored in: <bound method PhotoImage.__del__ of <tkinter.PhotoImage object at 0x0B411DB0>>

 Traceback (most recent call last):

   File "C:\Python34\lib\tkinter\__init__.py", line 3383, in __del__

     self.tk.call('image', 'delete', self.name)

 RuntimeError: main thread is not in main loop

Tcl_AsyncDelete: async handler deleted by the wrong thread

I am new to python and also to kivy so i cant really get what is the problem.

I tried the new thread outside the root gui class. I tried it outside the root class. Everytime the same.

Maybe the problem is that i dont really understand the deep working of GUIs. How Imagine it is that GUI is the main thread, so if I open Graph, GUI must stops ltill the graph is closed... That works. So I dont really understand why it crashes when I create paralel thread that process the Graph.

Thanks for reading

    Martin

 

PS: if the code is needed

Sorry for lame code:

class STORAGEofVARIABLES():
    COLORS={'red':'r','yellow':'y','blue':'b','green':'g','magenta':'m','black':'k','cyan':'c'}
    pass

STORAGE=STORAGEofVARIABLES()





class gui(BoxLayout):
    PlotActive=0
    COLORS={'red':'r','yellow':'y','blue':'b','green':'g','magenta':'m','black':'k','cyan':'c'}
    ##VALUES

    def __init__(self, *args, **kwargs):
        super(gui, self).__init__(*args, **kwargs)
        #Clock.schedule_interval(self.Thr, 1.5)

    def Thr(self):
        print('------')
        print('Number of Active Threads:' + str(threading.active_count()))
        print('Current working Thread: '+str(threading.current_thread().name))
        print('------')






    def save_values(self):
        OsaX = self.ids.OsaX
        OsaY = self.ids.OsaY
        Hodnota=self.ids.slajd
        Code=self.ids.codas
        COLORKA=self.ids.spin
        MARKER=self.ids.MarkSpinner
        GRID=self.ids.grid
        TLEGEND=self.ids.tlegenda
        LEGEND=self.ids.legenda
        TITLEGRAPH=self.ids.Titlegraph
        STORAGE.Y_LABEL = OsaY.text
        STORAGE.X_LABEL = OsaX.text
        STORAGE.TITLE_LABEL = TITLEGRAPH.text
        STORAGE.CODE = Code.text
        STORAGE.SLIDER_VALUE = Hodnota.value
        STORAGE.GRID = GRID.active
        STORAGE.TLEGEND = TLEGEND.text
        STORAGE.LEGEND = LEGEND.active
        STORAGE.COLORKA = COLORKA.text
        STORAGE.MARKER=MARKER.text
        STORAGE.PlotActive = threading.active_count()
        STORAGE.MARKER=MARKER.text

        Thread() # Start the thread






def Thread():
    t = threading.Thread(target=BasicGraph)
    t.daemon = True
    t.start()

def BasicGraph():
    x, y = [], []
    loc = {}
    try:
        exec(STORAGE.CODE, {}, loc)
        x = loc['x']
        y = loc['y']
    except:
        print("Chyba v kodu")
    plt.plot(x, y, label=STORAGE.TLEGEND, marker=STORAGE.MARKER, linewidth=STORAGE.SLIDER_VALUE,
             color=STORAGE.COLORS[STORAGE.COLORKA])
    if STORAGE.LEGEND == True:
        plt.legend()
    if STORAGE.GRID == True:
        plt.grid(color=STORAGE.COLORS[STORAGE.COLORKA])
    plt.title(STORAGE.TITLE_LABEL)
    plt.xlabel(STORAGE.X_LABEL)
    plt.ylabel(STORAGE.Y_LABEL)
    print(STORAGE.PlotActive) # HOW MANY THREADS ACTIVE
    if STORAGE.PlotActive == 1:
        plt.show()
    else:
        plt.draw()


class MainWindowApp(App):
    pass

if __name__=='__main__':
    MainWindowApp().run()

[Martin Fayad]

NOTE: It seems that if i make the new thread with something else than MatPlotLib graph, it works fine

[Bill Janssen]

I tried running this, but it seems to be missing some pieces, particullarly import statements.

Bill

[Bill Janssen]

But the problem seems clear:  you can't run the tkinter matplotlib backend in anything other than the main loop.  And I doubt that you can use the Kivy mainloop with the Tk libraries.  You've got to use Tk.mainloop().

Better to try the matplotlib backend from the Kivy Garden.  Even there, though, any code which updates the plot needs to be run on the Kivy main thread.

Bill

On Tuesday, August 9, 2016 at 4:54:58 AM UTC-7, Martin Fayad wrote:

[Martin Fayad]

So if I understand it well, the matplotlib window that opens behaves basicly like another gui as it uses tkinter and therefore there are two GUIs running in the same time?

Anyway - I attach the whole folder with the codes