Matplotlib Crashing tkinter Application

I am building an application that embeds a matplotlib figure into the GUI. The problem is that my app is crashing as soon as I add anything from matplotlib into my code (except for the imports, those work as usual). The problem occurs in my class Solver_App at tk.Tk.__init__(self, *args, **kwargs). When I run the code, I get a massive error and the app crashes. Here is some of my code:

import tkinter as tk
from tkinter import ttk

import matplotlib
from matplotlib import pyplot as plt
from mpl_toolkits.mplot3d import Axes3D
from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg, NavigationToolbar2TkAgg
from matplotlib.figure import Figure

# Setting up figures for integration in GUI:
fig_3D = plt.figure()
fig_2D = plt.figure()
a_3D = fig_3D.add_subplot(111, projection="3d")
a_2D = fig_2D.add_subplot(111)
a_3D.plot_wireframe([1, 2, 3, 4, 5], [1, 3, 7, 6, 4], [1, 2, 3, 4, 5], color="blue")

class Solver_App(tk.Tk, ttk.Frame):

    def __init__(self, *args, **kwargs):

        tk.Tk.__init__(self, *args, **kwargs)  # This is where the app crashes.

        # Equation frame holds everything related to the input and configuration of the equations.
        equation_frame = ttk.Frame(self)
        equation_frame.pack(side="bottom", fill="x", pady=50, padx=50)

        # More code goes here...

# There are more classes with a similar setup as the one above...

app = Solver_App()
app.mainloop()

And here is the massive error I get when running the code:

2015-08-14 15:18:29.142 Python[50796:18837594] -[NSApplication _setup:]: unrecognized selector sent to instance 0x10216a830
2015-08-14 15:18:29.143 Python[50796:18837594] An uncaught exception was raised
2015-08-14 15:18:29.143 Python[50796:18837594] -[NSApplication _setup:]: unrecognized selector sent to instance 0x10216a830
2015-08-14 15:18:29.144 Python[50796:18837594] (
    0   CoreFoundation                      0x00007fff9901b03c __exceptionPreprocess + 172
    1   libobjc.A.dylib                     0x00007fff9436476e objc_exception_throw + 43
    2   CoreFoundation                      0x00007fff9901e0ad -[NSObject(NSObject) doesNotRecognizeSelector:] + 205
    3   CoreFoundation                      0x00007fff98f63e24 ___forwarding___ + 1028
    4   CoreFoundation                      0x00007fff98f63998 _CF_forwarding_prep_0 + 120
    5   Tk                                  0x00000001024ad527 TkpInit + 476
    6   Tk                                  0x0000000102427aca Tk_Init + 1788
    7   _tkinter.so                         0x00000001006e5f2d Tcl_AppInit + 77
    8   _tkinter.so                         0x00000001006e30d6 Tkinter_Create + 934
    9   Python                              0x00000001000e44ce PyEval_EvalFrameEx + 28894
    10  Python                              0x00000001000e5ced PyEval_EvalCodeEx + 2349
    11  Python                              0x000000010003e8ba function_call + 186
    12  Python                              0x000000010000d3c8 PyObject_Call + 104
    13  Python                              0x00000001000e0cb9 PyEval_EvalFrameEx + 14537
    14  Python                              0x00000001000e5ced PyEval_EvalCodeEx + 2349
    15  Python                              0x000000010003e8ba function_call + 186
    16  Python                              0x000000010000d3c8 PyObject_Call + 104
    17  Python                              0x000000010002802c method_call + 140
    18  Python                              0x000000010000d3c8 PyObject_Call + 104
    19  Python                              0x000000010007b831 slot_tp_init + 81
    20  Python                              0x0000000100072d14 type_call + 212
    21  Python                              0x000000010000d3c8 PyObject_Call + 104
    22  Python                              0x00000001000e1b09 PyEval_EvalFrameEx + 18201
    23  Python                              0x00000001000e5ced PyEval_EvalCodeEx + 2349
    24  Python                              0x00000001000e5daf PyEval_EvalCode + 63
    25  Python                              0x000000010011048e PyRun_FileExFlags + 206
    26  Python                              0x000000010011083d PyRun_SimpleFileExFlags + 717
    27  Python                              0x000000010012810e Py_Main + 3262
    28  Python                              0x0000000100000e32 Python + 3634
    29  Python                              0x0000000100000c84 Python + 3204
    30  ???                                 0x0000000000000002 0x0 + 2
)
2015-08-14 15:18:29.144 Python[50796:18837594] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSApplication _setup:]: unrecognized selector sent to instance 0x10216a830'
*** First throw call stack:
(
    0   CoreFoundation                      0x00007fff9901b03c __exceptionPreprocess + 172
    1   libobjc.A.dylib                     0x00007fff9436476e objc_exception_throw + 43
    2   CoreFoundation                      0x00007fff9901e0ad -[NSObject(NSObject) doesNotRecognizeSelector:] + 205
    3   CoreFoundation                      0x00007fff98f63e24 ___forwarding___ + 1028
    4   CoreFoundation                      0x00007fff98f63998 _CF_forwarding_prep_0 + 120
    5   Tk                                  0x00000001024ad527 TkpInit + 476
    6   Tk                                  0x0000000102427aca Tk_Init + 1788
    7   _tkinter.so                         0x00000001006e5f2d Tcl_AppInit + 77
    8   _tkinter.so                         0x00000001006e30d6 Tkinter_Create + 934
    9   Python                              0x00000001000e44ce PyEval_EvalFrameEx + 28894
    10  Python                              0x00000001000e5ced PyEval_EvalCodeEx + 2349
    11  Python                              0x000000010003e8ba function_call + 186
    12  Python                              0x000000010000d3c8 PyObject_Call + 104
    13  Python                              0x00000001000e0cb9 PyEval_EvalFrameEx + 14537
    14  Python                              0x00000001000e5ced PyEval_EvalCodeEx + 2349
    15  Python                              0x000000010003e8ba function_call + 186
    16  Python                              0x000000010000d3c8 PyObject_Call + 104
    17  Python                              0x000000010002802c method_call + 140
    18  Python                              0x000000010000d3c8 PyObject_Call + 104
    19  Python                              0x000000010007b831 slot_tp_init + 81
    20  Python                              0x0000000100072d14 type_call + 212
    21  Python                              0x000000010000d3c8 PyObject_Call + 104
    22  Python                              0x00000001000e1b09 PyEval_EvalFrameEx + 18201
    23  Python                              0x00000001000e5ced PyEval_EvalCodeEx + 2349
    24  Python                              0x00000001000e5daf PyEval_EvalCode + 63
    25  Python                              0x000000010011048e PyRun_FileExFlags + 206
    26  Python                              0x000000010011083d PyRun_SimpleFileExFlags + 717
    27  Python                              0x000000010012810e Py_Main + 3262
    28  Python                              0x0000000100000e32 Python + 3634
    29  Python                              0x0000000100000c84 Python + 3204
    30  ???                                 0x0000000000000002 0x0 + 2
)
libc++abi.dylib: terminating with uncaught exception of type NSException

I have been referencing code from a tutorial [found here](http://pythonprogramming.net/how-to-embed-matplotlib-graph-tkinter-gui/"How to embed a Matplotlib graph to your Tkinter GUI"), but their example seems to work fine. What is causing this problem and how can it be fixed?

I am using Python 3.4, matplotlib 1.4.3, and running Mac OS Yosemite.

You need to set the TkAgg backend explicitly. I could reproduce your bug. With the following code, the problem is resolved.

import matplotlib
matplotlib.use("TkAgg")
from matplotlib import pyplot as plt

Note that setting the TkAgg backend after importing pyplot does not work either; it crashes too. You need to set it before importing pyplot. (Tested with MPL 1.4.3, tkinter.TkVersion 8.6)

If you don't want to edit the code, you can use set the following environment variable that matplotlib is reading: