This is in case someone is having the same problem on Ubuntu 14.04, as I did using Python 3.4.3. By using bits and hints from JDong's answer, I've solved the problem as follows. (Basically change the MatPlotLib backend to qt5agg.)

• Install python3-pyqt5.
• sudo apt-get install python3-pyqt5
• Find out where the matplotlibrc file is so you can edit it. This can be done using the following in Python console.
• import matplotlib
• matplotlib.matplotlib_fname()
• Edit the matplotlibrc file (you'll probably require sudo), find the line beginning with backend :, and change it to backend : qt5agg.
• If such a line doesn't exist, just create one.

The above steps have solved it for me on Ubuntu 14.04. I hope that helps.

• 安装python3-pyqt5

sudo apt-get install python3-pyqt5

• 找到matplotlibrc文件

打开python console import matplotlib matplotlib.matplotlib_fname()

• 编辑matplotlibrc文件

sudo vim [matplotlibrc file path]

• 找到backend变量将值改为qt5agg