最近服务器系统重装了一下，原来跑得好好的程序出现了一个“TclError: no display name and no $DISPLAY environment variable”错误，百思不得其解，搜了很久，终于找到了解决办法，记录如下：

DISPLAY error matplotlib

When error occur about this "$DISPLAY not set" when you run Python code that use matplotlib this happened because your matplotlib backend is set to FltkAgg, GTK, GTKAgg, GTKCairo, TkAgg , Wx or WxAgg they required a GUI that why error occur.

To solve this you must specific other backend that not required GUI (Agg, Cairo, PS, PDF or SVG ) when use matplotlib like this

• In code
  import matplotlib
  matplotlib.use('Agg')
• In command line use -d option
  Python subplot_demo.py -dAgg
  
  Remember when call savefig('filename') don't give it extension this will handle by backend that you specific e.g Agg will create file filename.png
  
  source from --> http://matplotlib .sourceforge.net/backends.html

资料来源：http://chewpichai.blogspot.com/2008/01/display-error-matplotlib.html 。原文可能被墙了，需要设法翻一下。