清除包含Matplotlib图的tkinter画布

Question

I am making a User Interface where the user has to put data in a frame, then clicking a button creates a Matplotlib interface. I was able to make it work, and my graph shows up along with the toolbar.

But when I click the button again, I can't get the other graph to go away. I saw I could use the .delete to clear the canvas. Putting it as the first line of the function will give me the "'canvas' used before assignement". I tried putting it as global but that didn't seem to work either.

Here is the problematic part of the code:

def graphiqueMatplot():
    #Not included: computation of the coordinates xS, yS,...
    f = Figure(figsize=(5,5), dpi=100)
    canvas = FigureCanvasTkAgg(f, master=courbe)
    a = f.add_subplot(111)
    a.plot(xS, yS)
    a.plot(xT, yT)
    a.plot(xL, yL)

    a.axis('tight')

    canvas.show()
    canvas.get_tk_widget().pack(side='top', fill=Y, expand=1)
    toolbar = NavigationToolbar2TkAgg( canvas, courbe )
    toolbar.update()
    canvas._tkcanvas.pack(side=Tk.TOP, fill=Tk.BOTH, expand=1)

#Main Program
cadreSimulation=Labelframe(root, text='Simulation')
courbe=Canvas(cadreSimulation, height=500, width=500, cursor='trek')

boutonGraphiqueMatplot=Button(cadreSimulation, text='Launch Matplotlib', command=graphiqueMatplot)
boutonGraphiqueMatplot.pack(side='top', fill='x')

courbe.pack()

cadreSimulation.pack(side='left')

Are you able to help ? Thanks a lot !

I want to add that I am a begginer with programmation, and not a native english speaker, so if you see any mistake concerning those don't hesitate telling me !

Answer 1

You have two main options here.

1. Create the FigureCanvasTkAgg object outside the graphiqueMatplot() function, have that function take that object as a parameter, and then have the function reconfigure the canvas with the new graph.

---

canvas = FigureCanvasTkAgg(f, master=courbe)
# more canvas creation and packing
...

boutonGraphiqueMatplot=Button(cadreSimulation, text='Launch Matplotlib',
                              command=lambda: graphiqueMatplot(canvas))
...

def graphiqueMatplot(c):
    f = Figure(figsize=(5,5), dpi=100)
    c.config(figure=f) # this is how tkinter objects are reconfigured,
                       # but it may be different for FigureCanvasTkAgg objects!
    a = f.add_subplot(111)
    # more plotting statements here

2. Try the delete() function like you wanted to, catching the exception:

---

def graphiqueMatplot():
    #Not included: computation of the coordinates xS, yS,...
    try:
        delete canvas/objects # use the delete method here
    except:
        pass # leave this as pass, so it takes no action if there's an error
    f = Figure(figsize=(5,5), dpi=100)
    canvas = FigureCanvasTkAgg(f, master=courbe)
    ...