mac系统，安装了matplotlib之后， 导入matplotlib.pyplot的时候报错
RuntimeError: Python is not installed as a framework. The Mac OS X backend will not be able to function correctly
if Python is not installed as a framework. See the Python documentation for more information on installing Python as a
framework on Mac OS X. Please either reinstall Python as a framework, or try one of the other backends. If you are using (Ana)Conda
please install python.app and replace the use of 'python' with 'pythonw'. See 'Working with Matplotlib on OSX' in the Matplotlib FAQ
for more information.
说python不是作为框架安装的，从stackoverflow上面找到的解决办法，现记录一下
1. cd ~/.matplotlib
2. nano matplotlibbrc
3. 在打开的文件里加一行： backend : TkAgg
nano编辑器的使用：ctrl + x 保存退出， y确认保存，回车退出
4. 在python里，使用matplotlib.pyplot之前先执行以下两行代码：
In [1]: import matplotlib In [2]: matplotlib.use("TkAgg")
然后再导入，import matplotlib.pyplot as plt
it works!